Drug Safety Evaluation
Expert Opin. Drug Saf. Downloaded from informahealthcare.com by Kainan University on 04/28/15 For personal use only.
A safety assessment of crizotinib in the treatment of ALK-positive NSCLC patients 1.
Introduction
2.
Pharmacokinetics and pharmacodynamics
3.
Safety of crizotinib
4.
Second-generation ALK inhibitors
5.
Conclusion
6.
Expert opinion
Alana Dikopf, Kevin Wood & Ravi Salgia† The University of Chicago Medicine, University of Chicago Medical Center, Chicago, IL, USA
Introduction: In the past decade, the treatment of NSCLC has been revolutionized by the discovery of key oncogenic driver mutations and the therapies that specifically target these mutations. Crizotinib has been shown to be an inhibitor of MET, anaplastic lymphoma kinase (ALK) and ROS1 receptor tyrosine kinases, and is FDA approved for ALK inhibition. Crizotinib is effective in NSCLC that harbors ALK translocations resulting in overexpression of oncogenic ALK fusion proteins. Areas covered: This paper will review crizotinib as a treatment for ALKpositive NSCLC. It will discuss the drug’s adverse events, drug--drug interactions and other important clinical and safety information related to crizotinib. Expert opinion: Compared to standard chemotherapy, crizotinib shows improved progression-free survival in ALK-positive NSCLC, with patient’s reporting improved quality of life. However, certain adverse events are more frequent with crizotinib versus standard chemotherapy and must be monitored for closely. The most common adverse events include ocular and gastrointestinal disturbances, cardiac and endocrine abnormalities, and peripheral edema. Many, though not all, of these side effects are likely due to the multiple tyrosine kinases inhibited by crizotinib, and will likely improve with second- and third-generation inhibitors that inhibit ALK more specifically. Keywords: adverse effects, anaplastic lymphoma kinase, crizotinib, drug safety, lung cancer, NSCLC Expert Opin. Drug Saf. (2015) 14(3):485-493
1.
Introduction
In 2015, there will be an estimated 221,200 new cases of lung cancer and 158,040 deaths [1]. While lung cancer continues to be the leading cause of cancer death worldwide, promising advances in personalized, targeted therapy have occurred in the past decade leading to significantly increased progression--freeand overall survival in certain lung cancer populations. In NSCLC in particular, we are becoming increasingly aware that this is a heterogeneous disease with multiple subtypes based on the specific oncogenic mutation that is driving cancer cell growth, as well as tumor suppressors that are deleted. The fusion gene, echinoderm microtubule--associated protein like 4 -- anaplastic lymphoma kinase (EML4-ALK), is an oncogene (once mutated or translocated with an enhancing partner) that is estimated to be present in 6% of NSCLC [2]. The ALK translocation was discovered for NSCLC in 2007 and consists of an inversion in chromosome 2 that juxtaposes the 5¢ end of the EML4 gene with the 3¢ end of the ALK gene [3,4]. The EML4 fusion partner results in constitutive kinase activity of the ALK tyrosine kinase, and in transgenic mouse models leads to the development of numerous lung adenocarcinomas [4]. Patients with ALK-rearranged NSCLC tend to be young (the average age at diagnosis is 50 years old), never- or light-smokers (< 10 packet years), with adenocarcinoma as the most common 10.1517/14740338.2015.1007040 © 2015 Informa UK, Ltd. ISSN 1474-0338, e-ISSN 1744-764X All rights reserved: reproduction in whole or in part not permitted
485
A. Dikopf et al.
Box 1. Drug summary. Drug name Phase Indication Pharmacology Route of administration Chemical structure
Crizotinib Launched Treatment of anaplastic lymphoma kinase (ALK)-positive metastatic NSCLC Inhibitor of Met, ALK and ROS-1 receptor tyrosine kinases Oral 3-[(1R)-1-(2,6-dichloro-3-fluorophenyl)ethoxy]-5-(1-piperidin-4-ylpyrazol-4-yl)pyridin-2-amine CI H3C NH2
F O
CI
Expert Opin. Drug Saf. Downloaded from informahealthcare.com by Kainan University on 04/28/15 For personal use only.
N
N
N
HN
Pivotal trial(s)
[8,14]
histology, and with no sex preference for males or females [5]. However, even though the phenotype is certainly clustered, all patients with adenocarcinomas should be tested for this alteration. When this mutation is present, NSCLC is extremely sensitive to ALK tyrosine kinase inhibitors. Crizotinib (Box 1), one such inhibitor, was approved for therapy against NSCLC with ALK translocations in 2011 and is now standard first-line treatment when this translocation is present [6]. Even if chemotherapy is given as first line, crizotinib is utilized for ALK-translocated patients. Crizotinib is an oral small-molecular tyrosine kinase inhibitor targeting ALK, c-MET and ROS1 tyrosine kinases (among others). The drug was originally developed as an inhibitor of c-MET, but was found to be a potent inhibitor of ALK activity and signal transduction [7]. Both in vitro and in vivo, crizotinib has been found to inhibit ALK cancer cells in the G1-S phase and to induce apoptosis of cancer cells [7]. Two key Phase III trials have demonstrated crizotinib to be superior to standard chemotherapy and associated with marked antitumor activity in patients with ALK-translocated NSCLC. Shaw et al. compared crizotinib to chemotherapy with either pemetrexed or docetaxel in previously treated patients and found a significant increase in progression-free survival (7.7 vs 3.0 months, p £ 0.001), though an interim analysis showed no improvement in overall survival [8]. Similar outcomes were seen in a trial of chemotherapy-naive patients, where progression-free survival in the crioztinib arm versus chemotherapy arm was 11 months versus 7 months in the chemotherapy arm (hazard ratio [HR] 0.45, 95% CI 0.35 -- 0.60). 486
While there was no difference in overall survival in this study, it is important to note at the time of progression that the chemotherapy patients were subsequently treated with crizotinib [9]. Since its approval in 2011, crizotinib has been found to be a generally well-tolerated drug in the treatment of lung cancer. However, there are certain toxicities associated with the drug that need to be acknowledged and monitored for when initiating treatment. This paper will review those toxicities and the dose modifications or treatments required when they develop. 2.
Pharmacokinetics and pharmacodynamics
To better understand the possible side effects and toxicities associated with crizotinib, it is important to understand the details of the drug’s metabolism. Crizotinib is an orally available, ATP-competitive, small-molecule tyrosine kinase inhibitor that comes in two dosage strengths, 250 and 200 mg. The recommended clinical dose in ALK NSCLC is 250 mg BID. In a Phase I study evaluating the pharmacokinetics of crizotinib, Li et al. demonstrated that after a single dose of 250 mg, the maximum concentration was achieved 4 h after the dose was taken, with a mean apparent terminal half-life of 42 h [10]. Interestingly, it was noted that maximum concentrations were slightly higher in Asian patients despite the same dosing; however, this was not felt to be clinically significant. The mean absolute bioavailability of crizotinib was 43% following administration of a single dose [11]. The solubility of crizotinib decreases with increasing pH; thus, drug administration must be done cautiously with other
Expert Opin. Drug Saf. (2015) 14(3)
Expert Opin. Drug Saf. Downloaded from informahealthcare.com by Kainan University on 04/28/15 For personal use only.
Crizotinib
drugs and foods (i.e., grapefruit and grapefruit juice) that can alter gastric pH. High-fat meals can also decrease the maximum concentration and AUC of crizotinib by up to 14% [11]. Crizotinib is a substrate of CYP3A and a moderate inhibitor of CYP3A and CYP2B6. It is primarily metabolized hepatically by the CYP3A4 and CYP3A5 systems. Drugs that are strong inhibitors or inducers of the CYP3A system should be avoided with crizotinib therapy, and dose reductions of CYP3A substrates may be necessary (Table 1 lists some of the common inhibitors and for a complete list the reader is referred to the package insert as well as other references) [11]. As crizotinib is hepatically metabolized, it is assumed that hepatic impairment likely increases plasma crizotinib concentrations, though data demonstrating this is lacking. Pharmacokinetic parameters are not altered by sex, or body weight, or renal impairment, though the drug has not been studied in patients with end-stage renal disease [11]. In some reports, it has been observed that crizotinib poorly penetrates the blood--brain barrier and the CNS system is thought to be a crizotinib ‘sanctuary.’ Costa et al. measured the concentration of crizotinib in both CSF and plasma and reported that the CSF-to-plasma ratio of crizotinib was only 0.0026 [12]. Thus, it makes sense that the sole site of initial progressive disease is most often the brain in patients being treated with crizotinib. We have also observed that there can be growth of ovary(ies) and/or uterus in the context of crizotinib as well as with metastasis de novo in ALK-translocated tumors [13]. As we learn more about the biology of ALKtranslocated tumors and efficacy of crizotinib, we must further study the mechanisms of metastasis as well as drug penetration in various organs. 3.
Safety of crizotinib
Crizotinib tends to be a well-tolerated drug. In the Phase III study comparing crizotinib to standard chemotherapy in previously treated ALK NSCLC patients, Shaw et al. used quality-of-life questionnaires and demonstrated a significant improvement in both progression-free survival and quality of life in the crizotinib arm [8]. Importantly, however, in the same study, more adverse events of any cause were reported in the crizotinib group (37% of patients reported serious adverse events in the crizotinib arm vs 23% in the chemotherapy arm). Dose reductions due to adverse reactions were required in 15% of patients, most commonly due to elevated alanine aminotransferase (ALT) elevation (7.6%), QTc prolongation (2.9%) and neutropenia (2.3%). Discontinuation of therapy was required in 17% of patients, most commonly due to interstitial lung disease (ILD) (1.7%), ALT and aspartate aminotransferase elevation (1.2%), dyspnea (1.2%), and pulmonary embolism (1.2%) [11]. Treatment-related adverse events leading to permanent discontinuation of the study drug occurred in 6% of the crizotinib patients and 10% of the chemotherapy patients. Treatment-related deaths occurred in three patients in the crizotinib arm (compared
to one patient in the chemotherapy arm). The deaths due to crizotinib were from a ventricular arrhythmia (n = 1) and from ILD (n = 2). The possible cause of the discrepancy between the improvement in quality of life in the crizotinib group despite an increase in reported side effects and dose reductions may be due to the fact that the safety analysis in this study did not adjust for the significantly longer duration patients were treated in crizotinib group compared to the chemotherapy group (median, 31 vs 12 weeks). In the initial Phase I study of crizotinib, side effects were common (reported in 97% of the 149 patients), though were most commonly grade 1 or 2 [14]. The most common adverse events were visual effects, nausea, diarrhea, constipation, vomiting and peripheral edema. The most common treatment-related grade 3 or 4 adverse events were neutropenia (n = 9), raised ALT (n = 6), hypophosphatemia (n = 6) and lymphopenia (n = 6). Except for peripheral edema, most of the side effects occurred early in therapy, with symptoms improving with time. The edema, on the other hand, appeared to be a late-onset cumulative adverse event. Adverse events that were reported in > 10% of patients in both of these studies are documented in Tables 2 and 3. Of note, it was observed that the Asian patients in the Phase I study had a higher frequency of adverse events compared to the non-Asian patients. This is thought to be related to the higher maximum concentration noted in Asian patients during the initial assessment of crizotinib pharmacokinetics. Interestingly, however, grade 3 or 4 adverse events, while rare, were more common in non-Asian patients [15]. Ocular disturbances Visual disturbances are the most commonly described adverse reaction associated with crizotinib therapy, reported in approximately 62% of cases [14,15]. Similar to other treatment-related side effects, visual disturbances are often transient and appear early during therapy, usually in the initial 2 weeks of treatment. The visual disturbances are most commonly characterized as trailing or flashing lights on moving objects during changes of ambient lighting from dark to light [16]. In the Phase II PROFILE 1005 study, these visual disturbances were generally transient, lasting up to 60 s, were not bothersome to the patient, had minimal impact of quality of life or activities of daily living, and did not require dose adjustment [15]. Severe or worsening vitreous floaters and/or photopsia could be signs of a retinal hole or impending retinal detachment and should be evaluated immediately. Given the risk for initial visual disturbances, patients should be advised to exercise caution when driving or operating machinery. Interestingly, while the physiological function of ALK in humans is unknown, in other organisms it is involved in the development of the visual and gut systems [17]. Thus, it was hypothesized that the common visual and gastrointestinal disturbances that occur with initial crizotinib therapy could be related to its anti-ALK effect within host tissues [13]. However, 3.1
Expert Opin. Drug Saf. (2015) 14(3)
487
A. Dikopf et al.
Expert Opin. Drug Saf. Downloaded from informahealthcare.com by Kainan University on 04/28/15 For personal use only.
Table 1. Common inhibitors, inducers and substrates of CYP3A to be avoided with crizotinib. CYP3A inhibitors
CYP3A inducers
CYP3A substrates
Ketoconazole Itraconazole Lopinavir/ritonavir Clarithromycin Indinavir/Ritonavir Conivaptan Voriconazole Nefazodone Grapefruit Juice
Avasimibe Carbamazepine Phenytoin Rifampin St. John’s wort Bosentan Efavirenz Etravirine Modafinil Nafcillin
Alfentanil Astemizole Cisapride Cyclosporine Dihydroergotamine Ergotamine Fentanyl Pimozide Quinidine Sirolimus Tacrolimus Terfenadine
Table 2. Treatment-related adverse events in 255 patients with anaplastic lymphoma kinase--translocated NSCLC treated on trials A8081001 and PROFILE 1005. All grades n (%)
Gastrointestinal disturbances The most common adverse effects observed are nausea (56.9%), diarrhea (48.6%) and vomiting (45.5%). Overall, < 1% of these effects are grade 3 or 4. The emetogenic potential of crizotinib is thought to be low to minimal [19]. In the Phase I trial of crizotinib, it was anecdotally noted that patient’s gastrointestinal symptoms appeared to improve when crizotinib was taken with food [13]. In our experience, when severe nausea and vomiting do occur that are not responsive to ondansetron or prochlorperazine, often administration of low-dose Ativan 0.5 mg orally 30 min prior to the crizotinib dose is found to be beneficial. 3.2
Cardiac disturbances While further investigations are needed, Doherty et al. demonstrated in human cardiomyocytes that crizotinib administration led to increased reactive oxygen species production, caspase activation, cholestorl accumulation, disruption in cardiac cell beat rate and blockage of ion channels [20]. These changes likely contribute to many of the adverse cardiac events that have been noted with crizotinib. 3.3
Grades 3 -- 4 n (%)
Significant (> 10%) adverse reactions associated with crizotinib therapy in 255 patients [24,41] Gastrointestinal Nausea 136 (53%) 0 Diarrhea 109 (43%) 0 Vomiting 101 (40%) 0 Constipation 69 (27%) 1 (< 1%) Esophageal disorder* 29 (11%) 0 General Edema 72 (28%) 0 Fatigue 51 (20%) 4 (2%) Decreased appetite 49 (19%) 0 Nervous system Dizziness 42 (16%) 0 Neuropathy 34 (13%) 1 (< 1%) Dysgeusia 30 (12%) 0 Liver Alanine transaminase increase 34 (13%) 14 (5%) 159 (62%) 0 Ocularz Skin Rash 25 (10%) 0 *Includes dyspepsia, dysphagia, epigastric discomfort/pain/burning, esophagitis, esophageal obstruction/pain/spasm/ulcer, gastroesophageal reflux, odynophagia and reflux esophagitis. z Includes diplopia, photopsia, photophobia, blurred vision, visual field defect, visual impairment, vitreous floaters, visual brightness and reduced visual acuity.
recent work by Liu et al. using in vivo electroretinogram to assess retinal functional changes in rats treated with crizotinib found a significant reduction in b-wave amplitude during the initial phase of dark adaption [18]. This change was not seen in rats treated with ceritinib (LDK378), a second-generation ALK-selective inhibitor. If the reduction in b-wave amplitude 488
is the cause of these visual changes, this would suggest that ALK inhibition is not involved and other mechanisms are leading to the ocular disturbances. It is possible that the inhibition of MET receptor tyrosine kinase may play a role in the retina.
Prolonged QTC Prolongation of the QTc interval has been demonstrated in 34 (2.7%) patients across clinical trials (n = 1225) [11]. A QTc > 500 ms was observed in 17 (1.4%) patients. It is recommended that crizotinib be avoided in patients with congenital long QT syndrome, and that periodic monitoring with electrocardiograms and electrolytes be done in patients with congestive heart failure, bradyarrhythmias, electrolyte abnormalities, and those taking medications known to prolong QT. Dosing adjustments are delineated according to QTc prolongation. For grade 3 QTc prolongation (> 500 ms), it is recommended to hold therapy and resume once the QTc interval is < 470 ms and restart dosing at 200 mg by mouth twice daily. If QTc prolongation occurs again, therapy should be restarted at 250 mg by mouth once daily once the interval returned to < 470 ms. For patients that have a prolonged interval recurrence despite a second dose adjustment, then the drug should be permanently discontinued. For any grade 4 QT prolongation (> 500 ms with life-threatening signs or symptoms of Torsades de pointes), it is recommended to permanently hold crizotinib [11]. 3.3.1
Bradycardia Crizotinib use has also demonstrated the potential for profound bradycardia (< 45 beats per minute) in approximately 5% of patients [21]. Importantly, all of the patients who developed bradycardia maintained a normal blood pressure and 3.3.2
Expert Opin. Drug Saf. (2015) 14(3)
Crizotinib
Table 3. Liver enzyme abnormalities. Step 1: evaluate total biliubin
Step 2: evaluate transaminases
Step 3: dosing modifications
£ 1.5 the upper limits of normal
ALT or AST > 5 the upper limit of the normal
Discontinue therapy, allow enzymes to recover to baseline or £ 3 times the upper limit of normal and then reduce daily dose Increase frequency of testing, consider dose reduction Evaluate for cholestasis or hemolysis. Permanently discontinue crizotinib Evaluate for cholestasis or hemolysis. Increase frequency of testing, consider dose reduction
> 1.5 the upper limits of normal
ALT or AST < 5 the upper limit of the normal ALT or AST > 3 the upper limit of the normal ALT or AST < 3 the upper limit of the normal
Expert Opin. Drug Saf. Downloaded from informahealthcare.com by Kainan University on 04/28/15 For personal use only.
ALT: Alanine aminotransferase; AST: Aspartate aminotransferase.
remained asymptomatic, thus not requiring a dose reduction [22]. This adverse event appears to be dose dependent; it has been observed that there is an average decrease in HR of 2.5 beats per minute per 100 ng/ml increase in crizotinib concentration [23]. Prior to the initiation of therapy, a thorough review of patient medications should be completed, with any agents that have the potential to promote or potentiate bradycardia eliminated or changed if possible. This includes b-blockers, calcium-channel blockers, digoxin, clonidine and other AV nodal blockers. Crizotinib should be discontinued in patients who are symptomatic and held until the heart rate is above 60 beats per minute. All medication profiles should be evaluated, and any medications that may potentiate bradycardia or hypotension should be stopped or dose reduced if feasible. If medications are identified that can be contributing to bradycardia and are stopped, crizotinib can be resumed at the same previous dose and heart rate should be closely monitored. If no medications are identified that contribute to bradycardia (or are identified, but cannot be stopped), crizotinib should be dose reduced and heart rate should be maintained to above 60 beats per minute while therapy continues. If patients experience life-threatening bradycardia, crizotinib should be permanently discontinued if no other contributing factors are identified. If patients experience life-threatening bradycardia, but another medication agent is identified as a contributing factor and is stopped or dose reduced, then crizotinib should be dose reduced to 250 mg by mouth once daily and cardiac function should be closely monitored. Heart rate should then be maintained at or above 60 beats per minute. Peripheral edema In addition to QTc prolongation and cardiac arrhythmias, crizotinib is related to the development of peripheral edema in 28% of patients [15,24]. As mentioned previously, this appears to be a late-onset, cumulative effect. This can usually be well managed with compression stockings and diuretics when appropriate. It is not related to a cardiomyopathy or decreased ejection fraction. The significantly lower incidence 3.3.3
of peripheral edema (8%) in a Phase I study of the secondgeneration ALK-inhibitor, ceretinib, suggests that an alternative pathway may be involved in causing the peripheral edema seen in crizotinib. One explanation could be inhibition of the c-met pathway, a pathway inhibited by crizotinib but not ceretinib. Supporting this is data from Tabernero et al., who evaluated the safety of Ficlatuzumab, a humanized hepatocyte growth factor (HGF) inhibitory monoclonal antibody that neutralizes HGF/c-Met binding and HGF-induced c-Met phosphorylation [25]. In a trial of 19 patients, 32% of patients developed peripheral edema, suggesting that c-Met pathway could be the primary etiology for peripheral edema with crizotinib. 3.4
Endocrine disturbances Hypogonadism
3.4.1
Two small studies have demonstrated the rapid suppression of testosterone (T) levels of men on crizotinib therapy [26,27]. In the largest study of 19 male patients, Weickhardt et al. observed that T levels in patients with metastatic NSCLC were significantly lower in patients receiving crizotinib than those who were not (mean T levels, 131 and 311 ng/dl, respectively, p = 0.002) [21]. In two patients, pretreatment T, follicle-stimulating hormone and leuteinizing hormone levels were measured and followed after initiation of therapy. A rapid decrease in all three levels was observed after 14 -- 21 days of therapy. These levels are observed to return to normal after discontinuation of crizotinib [21]. Hypogonadism is hypothesized to occur due to inhibition of the MET receptor, which is expressed in Leydig cells and, when activated by HGF, increases testosterone secretion and inhibits apoptosis of Leydig cells [28]. ALK receptors are expressed in the testes, though their function is unknown [29]. While we do recommend an endocrinologist’s involvement if concerning symptoms possibly related to low testosterone levels develop (such as fatigue, lack of erections, weight gain, etc.), the appropriateness of hormone replacement in the asymptomatic patient remains unclear and requires further studies. Other endocrine disruptions Though limited by small sample size, Sargis and Salgia observed in a group of seven patients that three patients were 3.4.2
Expert Opin. Drug Saf. (2015) 14(3)
489
Expert Opin. Drug Saf. Downloaded from informahealthcare.com by Kainan University on 04/28/15 For personal use only.
A. Dikopf et al.
hypocalcemic while on therapy [22]. The exact mechanism for this remains unclear. HGF has been noted to downregulate calcium-sensing receptors in rats [30], and it has been hypothesized that, through inhibition of MET and HGF, calcium-sensing receptors would be upregulated and thus parathyroid hormone levels would decrease leading to lower calcium levels [22]. However, two of the hypocalcemic patients in this study were noted to have elevated parathyroid hormone levels, so this is likely not the cause here. Regardless, the possibility of developing hypocalcemia with therapy should be noted and electrolyte levels periodically monitored. Interestingly, in the same study, it was observed that all seven patients had high or high-normal levels of IGF-1. This is an important growth factor that the pharmaceutical industry has tried to utilize in the treatment of cancer with little success thus far. The significance of elevated IGF-1 levels is limited by small sample size and needs to be studied in more detail with future studies. Hematologic disturbances In one Phase III study, grade 3 or 4 neutropenia and lymphopenia occurred in 12 and 9% of crizotinib-treated patients, respectively. Febrile neutropenia occurred in only one patient [8]. As with any chemotherapy or therapy that can reduce immunity, patients are to take proper precautions when receiving crizotinib to avoid infections and seek immediate medical attention if infection is suspected. 3.5
Hepatic disturbances Across multiple clinical trials, drug-induced hepatotoxicity was fatal in 2 (0.2%) of 1225 patients treated with crizotinib [11]. Elevations of ALT > 5 times the upper limit of normal occurred in 109 patients. Transaminitis generally occurs within the first 2 months of initiating therapy and it is recommended that liver function tests, including ALT and bilirubin, be monitored every 2 weeks during the first 2 months of therapy. The frequency of testing should be increased if any abnormalities are noted [11]. Crizotinib has not been studied in patients with baseline hepatic impairment. Current management guidelines for abnormal liver enzymes are demonstrated in Table 3. 3.6
Pulmonary disturbances Life-threatening ILD/pneumonitis can occur with crizotinib therapy. In 1225 patients across multiple clinical trials, 2.5% of patients developed ILD (any grade), 11 patients (0.9%) had grade 3 or 4, and 6 patients (0.5%) had fatal cases [11]. These cases generally occur in the first 2 months of therapy. In two case reports, ILD developed on days 14 and 25 of therapy [31,32]. If symptoms concerning for ILD develop while on therapy -- such as dyspnea, worsening cough, wheeze, hypoxia -- treatment should be halted and workup with the help of a pulmonologist should be initiated immediately. While there are case reports of successful 3.7
490
rechallenging with crizotinib [27,28], this is not recommended given that crizotinib-induced ILD can be life threatening and fatal. Dermatologic disturbances In clinical trials, rashes were reported in 9 -- 11% of patients, with no reported grade 3 or 4 rashes. However, there is one case report from 2014 of a patient developing a treatmentrelated grade 4 photosensitive rash on crizotinib therapy [33]. The rash resolved with cessation of therapy and recurred again with re-exposure to crizotinib. This type of rash, accompanied by exfoliation of skin and weeping, has not been reported to date in the literature and is the first case of grade IV rash reported. Patients receiving crizotinib that develop photosensitive dermatitis need to seek immediate treatment and be monitored accordingly. 3.8
Renal disturbances Renal cysts were noted to occur in 7% of patients treated with crizotinib in a Phase III clinical trial, compared to 1% of patients receiving standard chemotherapy [8]. The majority of the cysts were complex, and it was noted that local cystic invasion beyond the kidney did occur. The etiology of this remains unclear. 3.9
Fertility and breastfeeding Crizotinib is classified as pregnancy category D, and all patients should be counseled to utilize appropriate birth control methods while using crizotinib. This applies to patient’s undergoing treatment and their partners. No data is available regarding the use of crizotinib during pregnancy and during breastfeeding. Proper birth control should be utilized for at least 90 days post-use of crizotinib and patients should be closely monitored while receiving therapy [11]. 3.10
Patient counseling All patients must be counseled by a health-care professional regarding all the risks and benefits of using crizotinib. Patients must be made aware of potential adverse reactions and how to monitor for them. This article delineated major safety risks and patients should receive ample materials in addition to verbal counseling. In addition to safety counseling, patients should be advised on proper physician appointments and monitoring parameters. 3.11
4.
Second-generation ALK inhibitors
Despite an initial response to crizotinib, the majority of patients do relapse within 12 months owing to the development of resistance [34]. In this setting, possible options include a second-generation ALK inhibitor or a clinical trial. Ceritinib is a second-generation, oral, small-molecule, ATP-competitive tyrosine kinase inhibitor of ALK that has showed marked antitumor activity against both crizotinib-sensitive and
Expert Opin. Drug Saf. (2015) 14(3)
Expert Opin. Drug Saf. Downloaded from informahealthcare.com by Kainan University on 04/28/15 For personal use only.
Crizotinib
crizotinib-resistance tumors [35,36]. In enzymatic assays, ceritinib is 20 times as potent as crizotinib against ALK [32]. In a Phase I study evaluating the safety and pharmacokinetic properties of ceritinib, Shaw et al. demonstrated a safety profile similar to crizotinib [37]. Adverse events were primarily gastrointestinal and of a grade 1 -- 2. The gastrointestinal side effects did appear to occur more commonly in ceritinib patients -- drug-related diarrhea of grade 3 or 4 was reported in 9 of 130 patients (7%) treated with ceritinib, as compared with 0 of 321 patients treated with crizotinib. In addition, ceritinib had a higher incidence of grade 3 or 4 nausea than crizotinib (5% vs 1%). Four cases of ILD that resolved with discontinuation of ceritinib were noted. A total of 66 of 130 patients (51%) required at least one dose reduction. Further clinical trials of ceritinib are ongoing. More recently, a Phase I study of alectinib, another secondgeneration ALK inhibitor, was completed [38]. Alectinib appears to also be well tolerated, with fatigue (30%), myalgia (17%) and peripheral edema (15%) being the most common reported adverse events. The drug appears to be more efficacious than crizotinib at treating brain metastases -- 21 patients had CNS metastases at baseline, with 11 (52%) having an objective CNS response. Phase II studies are ongoing. Currently, the drug is only approved in Japan. 5.
Conclusion
The past decade marks a new, exciting era of personalized medicine in thoracic oncology. The strides that are being made in regard to developing novel and targeted therapeutic agents that prolong progression--free- and overall survival is very exciting. While the 6% of NSCLC cases affected by ALK rearrangement may seem insignificant at first, this represents over 60,000 patients annually and thus the ALK tyrosine kinase inhibitors provide an opportunity to make a dramatic change in the quality and duration of many patient’s lives [8]. Crizotinib represents the first of its kind to come on the market. Resistance does, inevitably, develop with this drug through multiple mechanisms. However, significant strides are being made to improve on crizotinib -- most notably with ceretinib, which has been shown to overcome crizotinib resistance in the majority of cases and was FDA approved as a second-line therapy in 2014. Recently, alectinib has also been approved in Japan to target ALK-translocated tumors that are resistant to crizotinib. While NSCLC patients treated with crizotinib appear to have improved quality of life compared to patients treated with standard chemotherapy, there are a multitude of side effects that can develop. These symptoms, most commonly visual or gastrointestinal, are usually grade 1 or 2 and improve with continued therapy [11]. It is important to note that, with an increasing number of patients being treated with crizotinib, numerous other drug interactions and adverse effects are being observed that were not noted in the initial clinical trials. Examples include
hormonal and electrolyte abnormalities, as well as grade IV hypersensitivity rashes. Thus, continued investigation into the safety profile of crizonitib will be important as we continue to improve on the treatment of ALK-translocated NSCLC. 6.
Expert opinion
The current development in the treatment of ALKtranslocated NSCLC is exciting, but there is still significant room for improvement. The medical academic community has recognized this, as demonstrated by the fact that there are currently numerous clinical trials worldwide evaluating ALK-translocated NSCLC [39]. It can be assumed that these clinical trials will improve on the current FDA-approved ALK tyrosine kinase inhibitors, crizotinib and ceretinib, both in terms of efficacy and safety profile. Crizotinib is an inhibitor of multiple tyrosine kinases, and it seems reasonable to assume that with the development of more specific inhibitors focused solely on the ALK tyrosine kinase, we can decrease patient side effects and improve the patient experience. For instance, data by Liu et al. suggest that c-MET inhibition may contribute to the peripheral edema commonly noted with crizotinib [18]. As mentioned, this adverse event was noted significantly less in a Phase I study of ceritinib, which more specifically inhibits ALK and does not inhibit c-MET. Crizotinib has also been found to be efficacious in multiple different other malignancies, including anaplastic large-cell lymphoma, diffuse large B-cell lymphoma, inflammatory myofibroblastic tumors, glioblastoma and neuroblastoma [40]. It will be interesting to observe how second- and thirdgeneration ALK inhibitors improve the efficacy of this targeted therapy in these malignancies. Crizotinib may also limited by its ability to potentially cross the blood--brain barrier and treat brain metastases as well as not penetrate the adnexa, and we predict in the coming years that the development of ALK tyrosine kinase that is able to do this will be developed. It will also be important to combine agents such as crizotinib and immune therapies. Treating metastatic lung cancer is a challenge, and with agents such as crizotinib, we have achieved a much better progression-free survival. Our next goal is to eradicate this disease completely. Interestingly, new side effects and adverse effects of crizotinib are coming to light as the patient population being treated with crizotinib increases. This is particularly true in regard to the hormonal changes, such as hypogonadism and increased IGF-1, which rapidly develop with the initiation of therapy. We predict with more patients being observed that we will be able to obtain more information behind the mechanisms of the hormonal changes and other systemic changes that occur due to crizotinib therapy. In doing so, we may be able to better understand the adverse effects that develop with treatment and find better ways of preventing or avoiding them. This is an incredible time in the world of thoracic oncology. Crizotinib represents one key example of the huge
Expert Opin. Drug Saf. (2015) 14(3)
491
A. Dikopf et al.
strides occurring in personalized, targeted treatment of lung cancer.
Declaration of interest The authors have received funding from the National Institute of Health and National Cancer Institute. They have Bibliography Papers of special note have been highlighted as either of interest () or of considerable interest () to readers.
Expert Opin. Drug Saf. Downloaded from informahealthcare.com by Kainan University on 04/28/15 For personal use only.
1.
2.
4.
Soda M, Takada S, Takeuchi K, et al. A mouse model for EML-4-ALK-positive lung cancer. Proc Natl Acad Sci USA 2008;105(50):19893
6.
7.
8.
..
492
9.
Soda M, Choi YL, Enomoto M, et al. Identification of the transforming EML4ALK fusion gene in non-small-cell lung cancer. Nature 2007;448:561-6 Shaw AT, Solomon B. Targeting anaplastic lymphoma kinase in lung cancer. Clin Cancer Res 2011;17(8):2081
5.
anaplastic lymphoma kinase (ALK) positive NSCLC.
American Cancer Society. Cancer facts & figures 2015. American Cancer Society; Atlanta: 2015
3.
Ou S-H, Bartlett CH, Mino-Kenudson M, et al. Crizotinib for the treatment of ALK-rearranged nonsmall cell lung cancer: a success story to usher in the second decade of molecular targeted therapy in oncology. Oncologist 2012;17(11):1351-75 Morales La Madrid A, Campbell N, Smith S, et al. Targeting ALK: a promising strategy for the treatment of non-small cell lung cancer, non-Hodgkin’s lymphoma, and neuroblastoma. Target Oncol 2012;7(3):199-210 Christensen JG, Zou HY, Arango ME, et al. Cytoreductive antitumor activity of PF-2341066, a novel inhibitor of anaplastic lymphoma kinase and c-Met, in experimental models of anaplastic large-cell lymphoma. Mol Cancer Ther 2007;6(12 Pt 1):3314 Shaw AT, Kim DW, Nakagawa K, et al. Crizotinib vs chemotherapy in advanced ALK-positive lung cancer. N Engl J Med 2013;368(25):2385 This Phase III study demonstrated crizotinib to have improved progression free survival and improved quality of life compared to standard chemotherapy for patients with
no relevant affiliations or financial involvement with any other organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.
Mok T, Kim DW, Wu YL, et al. First-line crizotinib versus pemetrexedcisplatin or pemetrexed-carboplatin in patients with advanced ALK-positive non-squamous non-small cell lung cancer (NSCLC): results of a phase III study (PROFILE 1014). J Clin Oncol 2014;32(5 Suppl):abstract 8002
10.
Li C, Alvey C, Bello A, et al. Pharmacokinetics (PK) of crizotinib (PF02341066) in patients with advanced non-small cell lung cancer (NSCLC) and other solid tumors. J Clin Oncol 2011;29(Suppl):abstract e13065
11.
Prescribing information. Xalkori (crizotinib) or capsules. Pfizer labs; New York, NY: August 2011
12.
Costa DB, Kobayashi S, Pandya SS, et al. CSF concentration of the anaplastic lymphoma kinase inhibitor crizotinib. J Clin Oncol 2011;29:e443-5
13.
14.
..
West AH, Yamada SD, Salgia R, et al. Unique metastases of ALK mutated lun cancer activated to the adnexa of the uterus. Case Rep Clin Pathol 2014;1(2):151-4 Camridge D, Bang YJ, Salgia R, et al. Activity and safety of crizotinib in patients with ALK-positive non-small cell lung cancer: updated results from a phase 1 study. Lancet Oncol 2012;13(10):1011-19 Important update on the safety of crizotinib from the Phase I study.
15.
Ou SHI, Salgia R, Clark J. Comparison of crizotinib (PF-02341066) pharmacokinetics between Asian and non-Asian patients with advanced malignancies. J Thorac Oncol 2010;5(Suppl 5):S382
16.
O’bryant CL, Wenger SD, Kim M, Thompson LA. Crizotinib: a new treatment option for ALK-positive nonsmall cell lung cancer. Ann Pharmacother 2013;47(2):189-97
Expert Opin. Drug Saf. (2015) 14(3)
17.
Palmer RH, Vernersson E, Grabbe C, et al. Anaplastic lymphoma kinase: signaling in development and disease. Biochem J 2009;420:345-61
18.
Liu CN, Mathialagan N, Lappin P, et al. Crizotinib reduces the rate of dark adaption in the rat retina independent of ALK inhibition. Toxicol Sci 2015;143(1):116-25
19.
Atkinson B, Barnett C, Choi S. Adult antiemetic management of chemotherapy-induced nausea and vomiting. The University of Texas M.D. Anderson Cancer Center, Houston, TX; 2013. Available from: http://www. mdanderson.org/education-and-research/ resources-for-professionals/clinical-toolsand-resources/practice-algorithms/clinmanagement-cinv-adult-web-algorithm. pdf [Last accessed 24 November 2014]
20.
Doherty K, Wappel R, Talbert D, et al. Multi-parameter in vitro toxcitiy testing of crizotinib, sunitinib, erlotinib, and nilotinib in human cardiomyocytes. Toxicol Appl Pharmacol 2013;272(1):245-55
21.
Sahu A, Prabhash K, Noronha V, et al. Crizotinib: a comprehensive review. South Asian J Cancer 2013;2(2):91-7
22.
Ou SH, Azada M, Dy J, Stiber J. Asymptomatic profound sinus bradycardia (Heart rate
Expert Opin. Drug Saf. Downloaded from informahealthcare.com by Kainan University on 04/28/15 For personal use only.
A safety assessment of crizotinib in the treatment of ALK-positive NSCLC patients 1.
Introduction
2.
Pharmacokinetics and pharmacodynamics
3.
Safety of crizotinib
4.
Second-generation ALK inhibitors
5.
Conclusion
6.
Expert opinion
Alana Dikopf, Kevin Wood & Ravi Salgia† The University of Chicago Medicine, University of Chicago Medical Center, Chicago, IL, USA
Introduction: In the past decade, the treatment of NSCLC has been revolutionized by the discovery of key oncogenic driver mutations and the therapies that specifically target these mutations. Crizotinib has been shown to be an inhibitor of MET, anaplastic lymphoma kinase (ALK) and ROS1 receptor tyrosine kinases, and is FDA approved for ALK inhibition. Crizotinib is effective in NSCLC that harbors ALK translocations resulting in overexpression of oncogenic ALK fusion proteins. Areas covered: This paper will review crizotinib as a treatment for ALKpositive NSCLC. It will discuss the drug’s adverse events, drug--drug interactions and other important clinical and safety information related to crizotinib. Expert opinion: Compared to standard chemotherapy, crizotinib shows improved progression-free survival in ALK-positive NSCLC, with patient’s reporting improved quality of life. However, certain adverse events are more frequent with crizotinib versus standard chemotherapy and must be monitored for closely. The most common adverse events include ocular and gastrointestinal disturbances, cardiac and endocrine abnormalities, and peripheral edema. Many, though not all, of these side effects are likely due to the multiple tyrosine kinases inhibited by crizotinib, and will likely improve with second- and third-generation inhibitors that inhibit ALK more specifically. Keywords: adverse effects, anaplastic lymphoma kinase, crizotinib, drug safety, lung cancer, NSCLC Expert Opin. Drug Saf. (2015) 14(3):485-493
1.
Introduction
In 2015, there will be an estimated 221,200 new cases of lung cancer and 158,040 deaths [1]. While lung cancer continues to be the leading cause of cancer death worldwide, promising advances in personalized, targeted therapy have occurred in the past decade leading to significantly increased progression--freeand overall survival in certain lung cancer populations. In NSCLC in particular, we are becoming increasingly aware that this is a heterogeneous disease with multiple subtypes based on the specific oncogenic mutation that is driving cancer cell growth, as well as tumor suppressors that are deleted. The fusion gene, echinoderm microtubule--associated protein like 4 -- anaplastic lymphoma kinase (EML4-ALK), is an oncogene (once mutated or translocated with an enhancing partner) that is estimated to be present in 6% of NSCLC [2]. The ALK translocation was discovered for NSCLC in 2007 and consists of an inversion in chromosome 2 that juxtaposes the 5¢ end of the EML4 gene with the 3¢ end of the ALK gene [3,4]. The EML4 fusion partner results in constitutive kinase activity of the ALK tyrosine kinase, and in transgenic mouse models leads to the development of numerous lung adenocarcinomas [4]. Patients with ALK-rearranged NSCLC tend to be young (the average age at diagnosis is 50 years old), never- or light-smokers (< 10 packet years), with adenocarcinoma as the most common 10.1517/14740338.2015.1007040 © 2015 Informa UK, Ltd. ISSN 1474-0338, e-ISSN 1744-764X All rights reserved: reproduction in whole or in part not permitted
485
A. Dikopf et al.
Box 1. Drug summary. Drug name Phase Indication Pharmacology Route of administration Chemical structure
Crizotinib Launched Treatment of anaplastic lymphoma kinase (ALK)-positive metastatic NSCLC Inhibitor of Met, ALK and ROS-1 receptor tyrosine kinases Oral 3-[(1R)-1-(2,6-dichloro-3-fluorophenyl)ethoxy]-5-(1-piperidin-4-ylpyrazol-4-yl)pyridin-2-amine CI H3C NH2
F O
CI
Expert Opin. Drug Saf. Downloaded from informahealthcare.com by Kainan University on 04/28/15 For personal use only.
N
N
N
HN
Pivotal trial(s)
[8,14]
histology, and with no sex preference for males or females [5]. However, even though the phenotype is certainly clustered, all patients with adenocarcinomas should be tested for this alteration. When this mutation is present, NSCLC is extremely sensitive to ALK tyrosine kinase inhibitors. Crizotinib (Box 1), one such inhibitor, was approved for therapy against NSCLC with ALK translocations in 2011 and is now standard first-line treatment when this translocation is present [6]. Even if chemotherapy is given as first line, crizotinib is utilized for ALK-translocated patients. Crizotinib is an oral small-molecular tyrosine kinase inhibitor targeting ALK, c-MET and ROS1 tyrosine kinases (among others). The drug was originally developed as an inhibitor of c-MET, but was found to be a potent inhibitor of ALK activity and signal transduction [7]. Both in vitro and in vivo, crizotinib has been found to inhibit ALK cancer cells in the G1-S phase and to induce apoptosis of cancer cells [7]. Two key Phase III trials have demonstrated crizotinib to be superior to standard chemotherapy and associated with marked antitumor activity in patients with ALK-translocated NSCLC. Shaw et al. compared crizotinib to chemotherapy with either pemetrexed or docetaxel in previously treated patients and found a significant increase in progression-free survival (7.7 vs 3.0 months, p £ 0.001), though an interim analysis showed no improvement in overall survival [8]. Similar outcomes were seen in a trial of chemotherapy-naive patients, where progression-free survival in the crioztinib arm versus chemotherapy arm was 11 months versus 7 months in the chemotherapy arm (hazard ratio [HR] 0.45, 95% CI 0.35 -- 0.60). 486
While there was no difference in overall survival in this study, it is important to note at the time of progression that the chemotherapy patients were subsequently treated with crizotinib [9]. Since its approval in 2011, crizotinib has been found to be a generally well-tolerated drug in the treatment of lung cancer. However, there are certain toxicities associated with the drug that need to be acknowledged and monitored for when initiating treatment. This paper will review those toxicities and the dose modifications or treatments required when they develop. 2.
Pharmacokinetics and pharmacodynamics
To better understand the possible side effects and toxicities associated with crizotinib, it is important to understand the details of the drug’s metabolism. Crizotinib is an orally available, ATP-competitive, small-molecule tyrosine kinase inhibitor that comes in two dosage strengths, 250 and 200 mg. The recommended clinical dose in ALK NSCLC is 250 mg BID. In a Phase I study evaluating the pharmacokinetics of crizotinib, Li et al. demonstrated that after a single dose of 250 mg, the maximum concentration was achieved 4 h after the dose was taken, with a mean apparent terminal half-life of 42 h [10]. Interestingly, it was noted that maximum concentrations were slightly higher in Asian patients despite the same dosing; however, this was not felt to be clinically significant. The mean absolute bioavailability of crizotinib was 43% following administration of a single dose [11]. The solubility of crizotinib decreases with increasing pH; thus, drug administration must be done cautiously with other
Expert Opin. Drug Saf. (2015) 14(3)
Expert Opin. Drug Saf. Downloaded from informahealthcare.com by Kainan University on 04/28/15 For personal use only.
Crizotinib
drugs and foods (i.e., grapefruit and grapefruit juice) that can alter gastric pH. High-fat meals can also decrease the maximum concentration and AUC of crizotinib by up to 14% [11]. Crizotinib is a substrate of CYP3A and a moderate inhibitor of CYP3A and CYP2B6. It is primarily metabolized hepatically by the CYP3A4 and CYP3A5 systems. Drugs that are strong inhibitors or inducers of the CYP3A system should be avoided with crizotinib therapy, and dose reductions of CYP3A substrates may be necessary (Table 1 lists some of the common inhibitors and for a complete list the reader is referred to the package insert as well as other references) [11]. As crizotinib is hepatically metabolized, it is assumed that hepatic impairment likely increases plasma crizotinib concentrations, though data demonstrating this is lacking. Pharmacokinetic parameters are not altered by sex, or body weight, or renal impairment, though the drug has not been studied in patients with end-stage renal disease [11]. In some reports, it has been observed that crizotinib poorly penetrates the blood--brain barrier and the CNS system is thought to be a crizotinib ‘sanctuary.’ Costa et al. measured the concentration of crizotinib in both CSF and plasma and reported that the CSF-to-plasma ratio of crizotinib was only 0.0026 [12]. Thus, it makes sense that the sole site of initial progressive disease is most often the brain in patients being treated with crizotinib. We have also observed that there can be growth of ovary(ies) and/or uterus in the context of crizotinib as well as with metastasis de novo in ALK-translocated tumors [13]. As we learn more about the biology of ALKtranslocated tumors and efficacy of crizotinib, we must further study the mechanisms of metastasis as well as drug penetration in various organs. 3.
Safety of crizotinib
Crizotinib tends to be a well-tolerated drug. In the Phase III study comparing crizotinib to standard chemotherapy in previously treated ALK NSCLC patients, Shaw et al. used quality-of-life questionnaires and demonstrated a significant improvement in both progression-free survival and quality of life in the crizotinib arm [8]. Importantly, however, in the same study, more adverse events of any cause were reported in the crizotinib group (37% of patients reported serious adverse events in the crizotinib arm vs 23% in the chemotherapy arm). Dose reductions due to adverse reactions were required in 15% of patients, most commonly due to elevated alanine aminotransferase (ALT) elevation (7.6%), QTc prolongation (2.9%) and neutropenia (2.3%). Discontinuation of therapy was required in 17% of patients, most commonly due to interstitial lung disease (ILD) (1.7%), ALT and aspartate aminotransferase elevation (1.2%), dyspnea (1.2%), and pulmonary embolism (1.2%) [11]. Treatment-related adverse events leading to permanent discontinuation of the study drug occurred in 6% of the crizotinib patients and 10% of the chemotherapy patients. Treatment-related deaths occurred in three patients in the crizotinib arm (compared
to one patient in the chemotherapy arm). The deaths due to crizotinib were from a ventricular arrhythmia (n = 1) and from ILD (n = 2). The possible cause of the discrepancy between the improvement in quality of life in the crizotinib group despite an increase in reported side effects and dose reductions may be due to the fact that the safety analysis in this study did not adjust for the significantly longer duration patients were treated in crizotinib group compared to the chemotherapy group (median, 31 vs 12 weeks). In the initial Phase I study of crizotinib, side effects were common (reported in 97% of the 149 patients), though were most commonly grade 1 or 2 [14]. The most common adverse events were visual effects, nausea, diarrhea, constipation, vomiting and peripheral edema. The most common treatment-related grade 3 or 4 adverse events were neutropenia (n = 9), raised ALT (n = 6), hypophosphatemia (n = 6) and lymphopenia (n = 6). Except for peripheral edema, most of the side effects occurred early in therapy, with symptoms improving with time. The edema, on the other hand, appeared to be a late-onset cumulative adverse event. Adverse events that were reported in > 10% of patients in both of these studies are documented in Tables 2 and 3. Of note, it was observed that the Asian patients in the Phase I study had a higher frequency of adverse events compared to the non-Asian patients. This is thought to be related to the higher maximum concentration noted in Asian patients during the initial assessment of crizotinib pharmacokinetics. Interestingly, however, grade 3 or 4 adverse events, while rare, were more common in non-Asian patients [15]. Ocular disturbances Visual disturbances are the most commonly described adverse reaction associated with crizotinib therapy, reported in approximately 62% of cases [14,15]. Similar to other treatment-related side effects, visual disturbances are often transient and appear early during therapy, usually in the initial 2 weeks of treatment. The visual disturbances are most commonly characterized as trailing or flashing lights on moving objects during changes of ambient lighting from dark to light [16]. In the Phase II PROFILE 1005 study, these visual disturbances were generally transient, lasting up to 60 s, were not bothersome to the patient, had minimal impact of quality of life or activities of daily living, and did not require dose adjustment [15]. Severe or worsening vitreous floaters and/or photopsia could be signs of a retinal hole or impending retinal detachment and should be evaluated immediately. Given the risk for initial visual disturbances, patients should be advised to exercise caution when driving or operating machinery. Interestingly, while the physiological function of ALK in humans is unknown, in other organisms it is involved in the development of the visual and gut systems [17]. Thus, it was hypothesized that the common visual and gastrointestinal disturbances that occur with initial crizotinib therapy could be related to its anti-ALK effect within host tissues [13]. However, 3.1
Expert Opin. Drug Saf. (2015) 14(3)
487
A. Dikopf et al.
Expert Opin. Drug Saf. Downloaded from informahealthcare.com by Kainan University on 04/28/15 For personal use only.
Table 1. Common inhibitors, inducers and substrates of CYP3A to be avoided with crizotinib. CYP3A inhibitors
CYP3A inducers
CYP3A substrates
Ketoconazole Itraconazole Lopinavir/ritonavir Clarithromycin Indinavir/Ritonavir Conivaptan Voriconazole Nefazodone Grapefruit Juice
Avasimibe Carbamazepine Phenytoin Rifampin St. John’s wort Bosentan Efavirenz Etravirine Modafinil Nafcillin
Alfentanil Astemizole Cisapride Cyclosporine Dihydroergotamine Ergotamine Fentanyl Pimozide Quinidine Sirolimus Tacrolimus Terfenadine
Table 2. Treatment-related adverse events in 255 patients with anaplastic lymphoma kinase--translocated NSCLC treated on trials A8081001 and PROFILE 1005. All grades n (%)
Gastrointestinal disturbances The most common adverse effects observed are nausea (56.9%), diarrhea (48.6%) and vomiting (45.5%). Overall, < 1% of these effects are grade 3 or 4. The emetogenic potential of crizotinib is thought to be low to minimal [19]. In the Phase I trial of crizotinib, it was anecdotally noted that patient’s gastrointestinal symptoms appeared to improve when crizotinib was taken with food [13]. In our experience, when severe nausea and vomiting do occur that are not responsive to ondansetron or prochlorperazine, often administration of low-dose Ativan 0.5 mg orally 30 min prior to the crizotinib dose is found to be beneficial. 3.2
Cardiac disturbances While further investigations are needed, Doherty et al. demonstrated in human cardiomyocytes that crizotinib administration led to increased reactive oxygen species production, caspase activation, cholestorl accumulation, disruption in cardiac cell beat rate and blockage of ion channels [20]. These changes likely contribute to many of the adverse cardiac events that have been noted with crizotinib. 3.3
Grades 3 -- 4 n (%)
Significant (> 10%) adverse reactions associated with crizotinib therapy in 255 patients [24,41] Gastrointestinal Nausea 136 (53%) 0 Diarrhea 109 (43%) 0 Vomiting 101 (40%) 0 Constipation 69 (27%) 1 (< 1%) Esophageal disorder* 29 (11%) 0 General Edema 72 (28%) 0 Fatigue 51 (20%) 4 (2%) Decreased appetite 49 (19%) 0 Nervous system Dizziness 42 (16%) 0 Neuropathy 34 (13%) 1 (< 1%) Dysgeusia 30 (12%) 0 Liver Alanine transaminase increase 34 (13%) 14 (5%) 159 (62%) 0 Ocularz Skin Rash 25 (10%) 0 *Includes dyspepsia, dysphagia, epigastric discomfort/pain/burning, esophagitis, esophageal obstruction/pain/spasm/ulcer, gastroesophageal reflux, odynophagia and reflux esophagitis. z Includes diplopia, photopsia, photophobia, blurred vision, visual field defect, visual impairment, vitreous floaters, visual brightness and reduced visual acuity.
recent work by Liu et al. using in vivo electroretinogram to assess retinal functional changes in rats treated with crizotinib found a significant reduction in b-wave amplitude during the initial phase of dark adaption [18]. This change was not seen in rats treated with ceritinib (LDK378), a second-generation ALK-selective inhibitor. If the reduction in b-wave amplitude 488
is the cause of these visual changes, this would suggest that ALK inhibition is not involved and other mechanisms are leading to the ocular disturbances. It is possible that the inhibition of MET receptor tyrosine kinase may play a role in the retina.
Prolonged QTC Prolongation of the QTc interval has been demonstrated in 34 (2.7%) patients across clinical trials (n = 1225) [11]. A QTc > 500 ms was observed in 17 (1.4%) patients. It is recommended that crizotinib be avoided in patients with congenital long QT syndrome, and that periodic monitoring with electrocardiograms and electrolytes be done in patients with congestive heart failure, bradyarrhythmias, electrolyte abnormalities, and those taking medications known to prolong QT. Dosing adjustments are delineated according to QTc prolongation. For grade 3 QTc prolongation (> 500 ms), it is recommended to hold therapy and resume once the QTc interval is < 470 ms and restart dosing at 200 mg by mouth twice daily. If QTc prolongation occurs again, therapy should be restarted at 250 mg by mouth once daily once the interval returned to < 470 ms. For patients that have a prolonged interval recurrence despite a second dose adjustment, then the drug should be permanently discontinued. For any grade 4 QT prolongation (> 500 ms with life-threatening signs or symptoms of Torsades de pointes), it is recommended to permanently hold crizotinib [11]. 3.3.1
Bradycardia Crizotinib use has also demonstrated the potential for profound bradycardia (< 45 beats per minute) in approximately 5% of patients [21]. Importantly, all of the patients who developed bradycardia maintained a normal blood pressure and 3.3.2
Expert Opin. Drug Saf. (2015) 14(3)
Crizotinib
Table 3. Liver enzyme abnormalities. Step 1: evaluate total biliubin
Step 2: evaluate transaminases
Step 3: dosing modifications
£ 1.5 the upper limits of normal
ALT or AST > 5 the upper limit of the normal
Discontinue therapy, allow enzymes to recover to baseline or £ 3 times the upper limit of normal and then reduce daily dose Increase frequency of testing, consider dose reduction Evaluate for cholestasis or hemolysis. Permanently discontinue crizotinib Evaluate for cholestasis or hemolysis. Increase frequency of testing, consider dose reduction
> 1.5 the upper limits of normal
ALT or AST < 5 the upper limit of the normal ALT or AST > 3 the upper limit of the normal ALT or AST < 3 the upper limit of the normal
Expert Opin. Drug Saf. Downloaded from informahealthcare.com by Kainan University on 04/28/15 For personal use only.
ALT: Alanine aminotransferase; AST: Aspartate aminotransferase.
remained asymptomatic, thus not requiring a dose reduction [22]. This adverse event appears to be dose dependent; it has been observed that there is an average decrease in HR of 2.5 beats per minute per 100 ng/ml increase in crizotinib concentration [23]. Prior to the initiation of therapy, a thorough review of patient medications should be completed, with any agents that have the potential to promote or potentiate bradycardia eliminated or changed if possible. This includes b-blockers, calcium-channel blockers, digoxin, clonidine and other AV nodal blockers. Crizotinib should be discontinued in patients who are symptomatic and held until the heart rate is above 60 beats per minute. All medication profiles should be evaluated, and any medications that may potentiate bradycardia or hypotension should be stopped or dose reduced if feasible. If medications are identified that can be contributing to bradycardia and are stopped, crizotinib can be resumed at the same previous dose and heart rate should be closely monitored. If no medications are identified that contribute to bradycardia (or are identified, but cannot be stopped), crizotinib should be dose reduced and heart rate should be maintained to above 60 beats per minute while therapy continues. If patients experience life-threatening bradycardia, crizotinib should be permanently discontinued if no other contributing factors are identified. If patients experience life-threatening bradycardia, but another medication agent is identified as a contributing factor and is stopped or dose reduced, then crizotinib should be dose reduced to 250 mg by mouth once daily and cardiac function should be closely monitored. Heart rate should then be maintained at or above 60 beats per minute. Peripheral edema In addition to QTc prolongation and cardiac arrhythmias, crizotinib is related to the development of peripheral edema in 28% of patients [15,24]. As mentioned previously, this appears to be a late-onset, cumulative effect. This can usually be well managed with compression stockings and diuretics when appropriate. It is not related to a cardiomyopathy or decreased ejection fraction. The significantly lower incidence 3.3.3
of peripheral edema (8%) in a Phase I study of the secondgeneration ALK-inhibitor, ceretinib, suggests that an alternative pathway may be involved in causing the peripheral edema seen in crizotinib. One explanation could be inhibition of the c-met pathway, a pathway inhibited by crizotinib but not ceretinib. Supporting this is data from Tabernero et al., who evaluated the safety of Ficlatuzumab, a humanized hepatocyte growth factor (HGF) inhibitory monoclonal antibody that neutralizes HGF/c-Met binding and HGF-induced c-Met phosphorylation [25]. In a trial of 19 patients, 32% of patients developed peripheral edema, suggesting that c-Met pathway could be the primary etiology for peripheral edema with crizotinib. 3.4
Endocrine disturbances Hypogonadism
3.4.1
Two small studies have demonstrated the rapid suppression of testosterone (T) levels of men on crizotinib therapy [26,27]. In the largest study of 19 male patients, Weickhardt et al. observed that T levels in patients with metastatic NSCLC were significantly lower in patients receiving crizotinib than those who were not (mean T levels, 131 and 311 ng/dl, respectively, p = 0.002) [21]. In two patients, pretreatment T, follicle-stimulating hormone and leuteinizing hormone levels were measured and followed after initiation of therapy. A rapid decrease in all three levels was observed after 14 -- 21 days of therapy. These levels are observed to return to normal after discontinuation of crizotinib [21]. Hypogonadism is hypothesized to occur due to inhibition of the MET receptor, which is expressed in Leydig cells and, when activated by HGF, increases testosterone secretion and inhibits apoptosis of Leydig cells [28]. ALK receptors are expressed in the testes, though their function is unknown [29]. While we do recommend an endocrinologist’s involvement if concerning symptoms possibly related to low testosterone levels develop (such as fatigue, lack of erections, weight gain, etc.), the appropriateness of hormone replacement in the asymptomatic patient remains unclear and requires further studies. Other endocrine disruptions Though limited by small sample size, Sargis and Salgia observed in a group of seven patients that three patients were 3.4.2
Expert Opin. Drug Saf. (2015) 14(3)
489
Expert Opin. Drug Saf. Downloaded from informahealthcare.com by Kainan University on 04/28/15 For personal use only.
A. Dikopf et al.
hypocalcemic while on therapy [22]. The exact mechanism for this remains unclear. HGF has been noted to downregulate calcium-sensing receptors in rats [30], and it has been hypothesized that, through inhibition of MET and HGF, calcium-sensing receptors would be upregulated and thus parathyroid hormone levels would decrease leading to lower calcium levels [22]. However, two of the hypocalcemic patients in this study were noted to have elevated parathyroid hormone levels, so this is likely not the cause here. Regardless, the possibility of developing hypocalcemia with therapy should be noted and electrolyte levels periodically monitored. Interestingly, in the same study, it was observed that all seven patients had high or high-normal levels of IGF-1. This is an important growth factor that the pharmaceutical industry has tried to utilize in the treatment of cancer with little success thus far. The significance of elevated IGF-1 levels is limited by small sample size and needs to be studied in more detail with future studies. Hematologic disturbances In one Phase III study, grade 3 or 4 neutropenia and lymphopenia occurred in 12 and 9% of crizotinib-treated patients, respectively. Febrile neutropenia occurred in only one patient [8]. As with any chemotherapy or therapy that can reduce immunity, patients are to take proper precautions when receiving crizotinib to avoid infections and seek immediate medical attention if infection is suspected. 3.5
Hepatic disturbances Across multiple clinical trials, drug-induced hepatotoxicity was fatal in 2 (0.2%) of 1225 patients treated with crizotinib [11]. Elevations of ALT > 5 times the upper limit of normal occurred in 109 patients. Transaminitis generally occurs within the first 2 months of initiating therapy and it is recommended that liver function tests, including ALT and bilirubin, be monitored every 2 weeks during the first 2 months of therapy. The frequency of testing should be increased if any abnormalities are noted [11]. Crizotinib has not been studied in patients with baseline hepatic impairment. Current management guidelines for abnormal liver enzymes are demonstrated in Table 3. 3.6
Pulmonary disturbances Life-threatening ILD/pneumonitis can occur with crizotinib therapy. In 1225 patients across multiple clinical trials, 2.5% of patients developed ILD (any grade), 11 patients (0.9%) had grade 3 or 4, and 6 patients (0.5%) had fatal cases [11]. These cases generally occur in the first 2 months of therapy. In two case reports, ILD developed on days 14 and 25 of therapy [31,32]. If symptoms concerning for ILD develop while on therapy -- such as dyspnea, worsening cough, wheeze, hypoxia -- treatment should be halted and workup with the help of a pulmonologist should be initiated immediately. While there are case reports of successful 3.7
490
rechallenging with crizotinib [27,28], this is not recommended given that crizotinib-induced ILD can be life threatening and fatal. Dermatologic disturbances In clinical trials, rashes were reported in 9 -- 11% of patients, with no reported grade 3 or 4 rashes. However, there is one case report from 2014 of a patient developing a treatmentrelated grade 4 photosensitive rash on crizotinib therapy [33]. The rash resolved with cessation of therapy and recurred again with re-exposure to crizotinib. This type of rash, accompanied by exfoliation of skin and weeping, has not been reported to date in the literature and is the first case of grade IV rash reported. Patients receiving crizotinib that develop photosensitive dermatitis need to seek immediate treatment and be monitored accordingly. 3.8
Renal disturbances Renal cysts were noted to occur in 7% of patients treated with crizotinib in a Phase III clinical trial, compared to 1% of patients receiving standard chemotherapy [8]. The majority of the cysts were complex, and it was noted that local cystic invasion beyond the kidney did occur. The etiology of this remains unclear. 3.9
Fertility and breastfeeding Crizotinib is classified as pregnancy category D, and all patients should be counseled to utilize appropriate birth control methods while using crizotinib. This applies to patient’s undergoing treatment and their partners. No data is available regarding the use of crizotinib during pregnancy and during breastfeeding. Proper birth control should be utilized for at least 90 days post-use of crizotinib and patients should be closely monitored while receiving therapy [11]. 3.10
Patient counseling All patients must be counseled by a health-care professional regarding all the risks and benefits of using crizotinib. Patients must be made aware of potential adverse reactions and how to monitor for them. This article delineated major safety risks and patients should receive ample materials in addition to verbal counseling. In addition to safety counseling, patients should be advised on proper physician appointments and monitoring parameters. 3.11
4.
Second-generation ALK inhibitors
Despite an initial response to crizotinib, the majority of patients do relapse within 12 months owing to the development of resistance [34]. In this setting, possible options include a second-generation ALK inhibitor or a clinical trial. Ceritinib is a second-generation, oral, small-molecule, ATP-competitive tyrosine kinase inhibitor of ALK that has showed marked antitumor activity against both crizotinib-sensitive and
Expert Opin. Drug Saf. (2015) 14(3)
Expert Opin. Drug Saf. Downloaded from informahealthcare.com by Kainan University on 04/28/15 For personal use only.
Crizotinib
crizotinib-resistance tumors [35,36]. In enzymatic assays, ceritinib is 20 times as potent as crizotinib against ALK [32]. In a Phase I study evaluating the safety and pharmacokinetic properties of ceritinib, Shaw et al. demonstrated a safety profile similar to crizotinib [37]. Adverse events were primarily gastrointestinal and of a grade 1 -- 2. The gastrointestinal side effects did appear to occur more commonly in ceritinib patients -- drug-related diarrhea of grade 3 or 4 was reported in 9 of 130 patients (7%) treated with ceritinib, as compared with 0 of 321 patients treated with crizotinib. In addition, ceritinib had a higher incidence of grade 3 or 4 nausea than crizotinib (5% vs 1%). Four cases of ILD that resolved with discontinuation of ceritinib were noted. A total of 66 of 130 patients (51%) required at least one dose reduction. Further clinical trials of ceritinib are ongoing. More recently, a Phase I study of alectinib, another secondgeneration ALK inhibitor, was completed [38]. Alectinib appears to also be well tolerated, with fatigue (30%), myalgia (17%) and peripheral edema (15%) being the most common reported adverse events. The drug appears to be more efficacious than crizotinib at treating brain metastases -- 21 patients had CNS metastases at baseline, with 11 (52%) having an objective CNS response. Phase II studies are ongoing. Currently, the drug is only approved in Japan. 5.
Conclusion
The past decade marks a new, exciting era of personalized medicine in thoracic oncology. The strides that are being made in regard to developing novel and targeted therapeutic agents that prolong progression--free- and overall survival is very exciting. While the 6% of NSCLC cases affected by ALK rearrangement may seem insignificant at first, this represents over 60,000 patients annually and thus the ALK tyrosine kinase inhibitors provide an opportunity to make a dramatic change in the quality and duration of many patient’s lives [8]. Crizotinib represents the first of its kind to come on the market. Resistance does, inevitably, develop with this drug through multiple mechanisms. However, significant strides are being made to improve on crizotinib -- most notably with ceretinib, which has been shown to overcome crizotinib resistance in the majority of cases and was FDA approved as a second-line therapy in 2014. Recently, alectinib has also been approved in Japan to target ALK-translocated tumors that are resistant to crizotinib. While NSCLC patients treated with crizotinib appear to have improved quality of life compared to patients treated with standard chemotherapy, there are a multitude of side effects that can develop. These symptoms, most commonly visual or gastrointestinal, are usually grade 1 or 2 and improve with continued therapy [11]. It is important to note that, with an increasing number of patients being treated with crizotinib, numerous other drug interactions and adverse effects are being observed that were not noted in the initial clinical trials. Examples include
hormonal and electrolyte abnormalities, as well as grade IV hypersensitivity rashes. Thus, continued investigation into the safety profile of crizonitib will be important as we continue to improve on the treatment of ALK-translocated NSCLC. 6.
Expert opinion
The current development in the treatment of ALKtranslocated NSCLC is exciting, but there is still significant room for improvement. The medical academic community has recognized this, as demonstrated by the fact that there are currently numerous clinical trials worldwide evaluating ALK-translocated NSCLC [39]. It can be assumed that these clinical trials will improve on the current FDA-approved ALK tyrosine kinase inhibitors, crizotinib and ceretinib, both in terms of efficacy and safety profile. Crizotinib is an inhibitor of multiple tyrosine kinases, and it seems reasonable to assume that with the development of more specific inhibitors focused solely on the ALK tyrosine kinase, we can decrease patient side effects and improve the patient experience. For instance, data by Liu et al. suggest that c-MET inhibition may contribute to the peripheral edema commonly noted with crizotinib [18]. As mentioned, this adverse event was noted significantly less in a Phase I study of ceritinib, which more specifically inhibits ALK and does not inhibit c-MET. Crizotinib has also been found to be efficacious in multiple different other malignancies, including anaplastic large-cell lymphoma, diffuse large B-cell lymphoma, inflammatory myofibroblastic tumors, glioblastoma and neuroblastoma [40]. It will be interesting to observe how second- and thirdgeneration ALK inhibitors improve the efficacy of this targeted therapy in these malignancies. Crizotinib may also limited by its ability to potentially cross the blood--brain barrier and treat brain metastases as well as not penetrate the adnexa, and we predict in the coming years that the development of ALK tyrosine kinase that is able to do this will be developed. It will also be important to combine agents such as crizotinib and immune therapies. Treating metastatic lung cancer is a challenge, and with agents such as crizotinib, we have achieved a much better progression-free survival. Our next goal is to eradicate this disease completely. Interestingly, new side effects and adverse effects of crizotinib are coming to light as the patient population being treated with crizotinib increases. This is particularly true in regard to the hormonal changes, such as hypogonadism and increased IGF-1, which rapidly develop with the initiation of therapy. We predict with more patients being observed that we will be able to obtain more information behind the mechanisms of the hormonal changes and other systemic changes that occur due to crizotinib therapy. In doing so, we may be able to better understand the adverse effects that develop with treatment and find better ways of preventing or avoiding them. This is an incredible time in the world of thoracic oncology. Crizotinib represents one key example of the huge
Expert Opin. Drug Saf. (2015) 14(3)
491
A. Dikopf et al.
strides occurring in personalized, targeted treatment of lung cancer.
Declaration of interest The authors have received funding from the National Institute of Health and National Cancer Institute. They have Bibliography Papers of special note have been highlighted as either of interest () or of considerable interest () to readers.
Expert Opin. Drug Saf. Downloaded from informahealthcare.com by Kainan University on 04/28/15 For personal use only.
1.
2.
4.
Soda M, Takada S, Takeuchi K, et al. A mouse model for EML-4-ALK-positive lung cancer. Proc Natl Acad Sci USA 2008;105(50):19893
6.
7.
8.
..
492
9.
Soda M, Choi YL, Enomoto M, et al. Identification of the transforming EML4ALK fusion gene in non-small-cell lung cancer. Nature 2007;448:561-6 Shaw AT, Solomon B. Targeting anaplastic lymphoma kinase in lung cancer. Clin Cancer Res 2011;17(8):2081
5.
anaplastic lymphoma kinase (ALK) positive NSCLC.
American Cancer Society. Cancer facts & figures 2015. American Cancer Society; Atlanta: 2015
3.
Ou S-H, Bartlett CH, Mino-Kenudson M, et al. Crizotinib for the treatment of ALK-rearranged nonsmall cell lung cancer: a success story to usher in the second decade of molecular targeted therapy in oncology. Oncologist 2012;17(11):1351-75 Morales La Madrid A, Campbell N, Smith S, et al. Targeting ALK: a promising strategy for the treatment of non-small cell lung cancer, non-Hodgkin’s lymphoma, and neuroblastoma. Target Oncol 2012;7(3):199-210 Christensen JG, Zou HY, Arango ME, et al. Cytoreductive antitumor activity of PF-2341066, a novel inhibitor of anaplastic lymphoma kinase and c-Met, in experimental models of anaplastic large-cell lymphoma. Mol Cancer Ther 2007;6(12 Pt 1):3314 Shaw AT, Kim DW, Nakagawa K, et al. Crizotinib vs chemotherapy in advanced ALK-positive lung cancer. N Engl J Med 2013;368(25):2385 This Phase III study demonstrated crizotinib to have improved progression free survival and improved quality of life compared to standard chemotherapy for patients with
no relevant affiliations or financial involvement with any other organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.
Mok T, Kim DW, Wu YL, et al. First-line crizotinib versus pemetrexedcisplatin or pemetrexed-carboplatin in patients with advanced ALK-positive non-squamous non-small cell lung cancer (NSCLC): results of a phase III study (PROFILE 1014). J Clin Oncol 2014;32(5 Suppl):abstract 8002
10.
Li C, Alvey C, Bello A, et al. Pharmacokinetics (PK) of crizotinib (PF02341066) in patients with advanced non-small cell lung cancer (NSCLC) and other solid tumors. J Clin Oncol 2011;29(Suppl):abstract e13065
11.
Prescribing information. Xalkori (crizotinib) or capsules. Pfizer labs; New York, NY: August 2011
12.
Costa DB, Kobayashi S, Pandya SS, et al. CSF concentration of the anaplastic lymphoma kinase inhibitor crizotinib. J Clin Oncol 2011;29:e443-5
13.
14.
..
West AH, Yamada SD, Salgia R, et al. Unique metastases of ALK mutated lun cancer activated to the adnexa of the uterus. Case Rep Clin Pathol 2014;1(2):151-4 Camridge D, Bang YJ, Salgia R, et al. Activity and safety of crizotinib in patients with ALK-positive non-small cell lung cancer: updated results from a phase 1 study. Lancet Oncol 2012;13(10):1011-19 Important update on the safety of crizotinib from the Phase I study.
15.
Ou SHI, Salgia R, Clark J. Comparison of crizotinib (PF-02341066) pharmacokinetics between Asian and non-Asian patients with advanced malignancies. J Thorac Oncol 2010;5(Suppl 5):S382
16.
O’bryant CL, Wenger SD, Kim M, Thompson LA. Crizotinib: a new treatment option for ALK-positive nonsmall cell lung cancer. Ann Pharmacother 2013;47(2):189-97
Expert Opin. Drug Saf. (2015) 14(3)
17.
Palmer RH, Vernersson E, Grabbe C, et al. Anaplastic lymphoma kinase: signaling in development and disease. Biochem J 2009;420:345-61
18.
Liu CN, Mathialagan N, Lappin P, et al. Crizotinib reduces the rate of dark adaption in the rat retina independent of ALK inhibition. Toxicol Sci 2015;143(1):116-25
19.
Atkinson B, Barnett C, Choi S. Adult antiemetic management of chemotherapy-induced nausea and vomiting. The University of Texas M.D. Anderson Cancer Center, Houston, TX; 2013. Available from: http://www. mdanderson.org/education-and-research/ resources-for-professionals/clinical-toolsand-resources/practice-algorithms/clinmanagement-cinv-adult-web-algorithm. pdf [Last accessed 24 November 2014]
20.
Doherty K, Wappel R, Talbert D, et al. Multi-parameter in vitro toxcitiy testing of crizotinib, sunitinib, erlotinib, and nilotinib in human cardiomyocytes. Toxicol Appl Pharmacol 2013;272(1):245-55
21.
Sahu A, Prabhash K, Noronha V, et al. Crizotinib: a comprehensive review. South Asian J Cancer 2013;2(2):91-7
22.
Ou SH, Azada M, Dy J, Stiber J. Asymptomatic profound sinus bradycardia (Heart rate
