ANTIMICROBiAL AGENTS AND CHEMOTHERAPY, Dec. 1992, p. 2661-2663

Vol. 36, No. 12

0066-4804/92/122661-03$02.00/0 Copyright © 1992, American Society for Microbiology

Pharmacokinetics of R 82913 in AIDS Patients: a Phase I Dose-Finding Study of Oral Administration Compared with Intravenous Infusion STtPHANE DE WIT,1 PHILIPPE HERMANS,1 BERNADETIrE SOMMEREIJNS,1 O'DOHERTY,1 ROBERT WESTENBORGHS,2 VERA VAN DE VELDE,2 GEERT F. M. J. CAUWENBERGH,2 AND NATHAN CLUMECK"* Division of Infectious Diseases, St. Pierre University Hospital, Free University ofBrussels, B-1000 Brussels,' and Janssen Research Foundation, B-2340 Beerse,2 Belgium ELIZABETH

Received 3 December 1991/Accepted 5 October 1992

The pharmacokinetics of oral administration of R 82913, or tetrahydroimidazol [4,5,1-jkJ-benzodiazepin2(1H)-one or -thione (TIBO), was compared with those of intravenous administration in five AIDS patients. TIBO was administered as a single daily 1-h infusion of 100 mg for 29 days and orally as a single daily dose for 14 days with three consecutive regimens of 100, 200, and 100 mg with probenecid (1 g) daily. Each cycle was followed by a wash-out period. Oral bioavailability of TIBO appears to be low and is not improved by the adjunction of probenecid. Trough levels obtained with oral administration systematically remained far below the 90%o inhibitory concentration of TIBO against human immunodeficiency virus type 1 (HIV-1). Tolerance of TIBO was excellent. No clinical efficacy could be demonstrated. p24 antigenemia decreased significantly in one patient under intravenous therapy. TEBO derivatives are promising anti-HIV-i agents in vitro, but improvement of oral bioavailability is needed before implementation of long-term efficacy and tolerability studies. Moreover, rapid emergence of resistance, which has been recently documented, constitutes a major problem with most nonnucleoside reverse transcriptase inhibitors.

administered orally for 14 days during cycles 2, 3, and 4 at doses of, respectively, 100 mg once daily, 200 mg once daily, and 100 mg once daily in association with 250 mg of probenecid four times daily. Probenecid was added to assess whether levels of TIBO in plasma could be increased by reducing renal excretion. Each oral cycle was followed by a 7-day wash-out period. Pharmacokinetic studies were performed on the first and last days of each cycle. Venous blood samples were taken before infusion; at 0.5, 1 (end of infusion), 1.25, 1.5, 2, 4, 6, 8, 12, and 24 h after the start of the first and last infusions; and at 36, 48, 60, 72, 84, and 96 h after the last infusion (cycle 1). Venous blood samples were taken before and at 1, 2, 4, 6, 8, and 24 h after oral intake on the first and last days of cycles 2, 3, and 4. Peak and trough levels were measured twice weekly during each cycle. The blood samples were centrifuged, and separated plasma was stored at -20°C until assay. Plasma TIBO concentration was measured by specific high-performance liquid chromatography with UV detection as previously described. Detection sensitivity was 2.0 ng/ml (2). All pharmacokinetic parameters were determined for individual data. The peak concentrations in plasma at the end of the infusion and after oral dosing were assessed by visual inspection of the plasma concentration-time curve, and the terminal half-life was calculated as 0.693/3. The area under the curve (AUC) for a 24-h dosing interval (AUC,_2A) was determined by trapezoidal summation. The absolute oral bioavailability was calculated as 100 times the dose-normalized AUC ratio of the oral dose relative to the intravenous dose. Patients were seen at least twice weekly. Signs and symptoms were carefully recorded. Biochemical and hematological profiles were obtained at entry, once weekly during cycle 1, and on the last day of cycles 2, 3, and 4. p24 antigen

TIBO is member of a novel series of tetrahydroimidazol[4,5,1-jk]-benzodiazepin-2(lH)-one and -thione (TIBO) derivatives. These agents have been shown to inhibit the replication of human immunodeficiency virus type 1 (HIV-1) but not HIV-2 in vitro by a specific effect on reverse transcriptase (4). Daily intravenous administration of 120 to 200 mg of TIBO has been shown to lead to a trough concentration in plasma that is higher than the 90% inhibitory concentration of the drug for HIV-1 (20 to 40 ng/ml). Tolerance was excellent (3, 5). The aim of this study was to evaluate the pharmacokinetics and tolerability of orally administered TIBO compared with intravenously infused TIBO in AIDS patients. (This work was presented at the 31st Interscience Conference on Antimicrobial Agents and Chemotherapy, Chicago, Ill., October 1991.)

MATERIALS AND METHODS This open prospective study included five homosexual males with AIDS, aged 28 to 39 years, who previously had been treated with and become intolerant to zidovudine. All five patients had remained free of any antiretroviral or immunomodulatory agent for at least 2 weeks before entry. Their mean CD4 cell count at entry was 72 cells per ,ul (range, 44 to 135 cells per p.l). All patients were informed of the nature, duration, and purpose of the study before entry. The study protocol was approved by the hospital ethical committee. The study was divided into four cycles. During cycle 1, TIBO was administered intravenously at a dose of 100 mg in 1 h once daily for 29 days through a central venous catheter (Port-a-Cath). After a 14-day wash-out period, TIBO was *

Corresponding author. 2661

2662

DE WIT ET AL.

ANTIMICROB. AGENTS CHEMOTHER.

ngiml 1000 t~~~~~~~~-

i t

cylb 1:day 29

-

-~~~~~~. .._... cycle 2: day 14 cycle 3: day 14

itNs

10

0

6

12

IS

24

30

36

42

46

64

0

n

78

so Days

64

Hours

FIG. 1. Mean levels of R 82913 in plasma after the last dose.

measured twice weekly by enzyme-linked immunosorbent assay (Innotest HIV1, HIV2; Innogenetics, Antwerp, Belgium).

was

RESULTS Three patients completed the four cycles of the study. The two other patients were dropped before the end of the study,

after cycle 1 because of a diagnosis of lymphoma and after cycle 3 because of poor clinical status. Thus, 19 cycles leading to 38 pharmacokinetic profiles were completed. Plasma profiles of TIBO on the last day of each cycle are shown in Fig. 1. Maximal plasma concentration, AUCO24, and terminal half-life on the first and last days of each cycle are shown in Table 1. Absolute bioavailability after oral administration was 7 to 10%. Daily injections of 100 mg did not produce the trough TIBO concentration of 20 to 40 ng/ml that is required to protect against cytopathic effect of HIV in vitro. Monitoring of tolerability did not reveal any sign or symptom which could be related to TIBO administration. There were no changes in the biochemical or hematological profiles. p24 antigen profiles are shown in Fig. 2. Three patients had low p24 antigen level at entry that remained low throughout the study period. One patient had a p24 antigen level of 148 pg/ml at entry that remained unchanged under TIBO administration. One patient had a significant decrease during intravenous administration (cycle 1):250 pg/ml at entry and 58 pg/ml at the end. p24 antigen remained low for the 2-week wash-out period and then increased while TIBO one one

60

FIG. 2. Evolution of concentrations of p24 antigen in during cycles 1 through 4.

administered orally (cycle 2): 45 pg/ml and 178 pg/ml on the last day.

was

on

serum

the first day

DISCUSSION Various compounds that inhibit HIV replication through inhibition of reverse transcriptase have been described. Most of these compounds are nucleoside analogs such as zidovudine, ddI, and ddC. Zidovudine and ddI are the only drugs licensed in the United States and Europe as therapy for severe HIV infection. Zidovudine, ddI, and ddC are associated with side effects which are generally reversible or can be modulated by reducing drug dosage. Moreover, resistant strains of HIV have been shown to appear with these three drugs, which emphasizes the need for new therapeutic agents. Other nucleoside analogs such as FLT, d4T, and 3TC are currently under phase I or II investigation and have shown promising results in terms of activities and toxicity profiles (7). Various nonnucleoside reverse transcriptase inhibitors are very potent in vitro inhibitors of HIV-1. TIBO derivatives electively inhibit HIV-1 reverse transcriptase. In five cell systems, TIBO derivatives have been shown to inhibit HIV-1 but not HIV-2 in nanomolar amounts which were 104 to 105 times lower than the cytotoxic concentration. However, quick emergence of resistance against TIBO as well as other nonnucleoside reverse transcriptase inhibitors raises important questions regarding the future development of this class of anti-HIV agents (1, 6). In a dose-escalating pilot study, TIBO was administered intravenously to 22 patients with AIDS or AIDS-related complex. Daily intravenous injections of 120 to 200 mg were required to produce the trough TIBO level in plasma of 20 to

TABLE 1. Pharmacokinetics datae

Cycle

Dose and route

patients

No. of

Day Dy

Cm. (ng/ml) ± SD) (mean

AUCn±+ SD) SD (mean

0 29 0 14 0 14 0

457 542 17.5 25.0 59.0 67.0 21.4

1,117 1,600

1

100 mg i.v.

5

2

100 mg oral

4

3

200 mg oral

4

4 '

100 mg oral + 1 g of probenid 3 Cm., maximum concentration in plasma; tln, elimination half-life; i.v., intravenous.

± ± ± ± ± ± ±

88 142 7.3 23.1 31.0 47.7 13.8

72 103 171 247 81

± ± ± ± ± ± ±

279 832 38 84 74 110 40

Median t, (h) (range) 28 (11.3-70.2) Not evaluable Not evaluable Not evaluable Not evaluable Not evaluable

VOL. 36, 1992

40 ng/ml that is needed for inhibition of HIV cytopathogenicity in vitro. TIBO tolerability was excellent: a few patients noticed slight tiredness, but no significant clinical or biological side effect was reported. This study was not designed to assess efficacy: no clinical efficacy was shown, and the changes in CD4-cell levels and p24 antigenemia were heterogeneous among patients with poor prognoses (5). Long-term anti-HIV therapy through daily intravenous administration appears to be unrealistic. In this respect, good oral bioavailability is clearly needed for the development of any new anti-HIV agent. Our study demonstrates that oral bioavailability of TIBO is low (7 to 10%). Peak values range from 10.5 to 59.4 ng/ml with 100 mg given orally and from 22.3 to 121 ng/ml with 200 mg given orally without any advantage from added probenecid. Excretion of R 82913 occurs through metabolism, with a very low urinary excretion of unchanged compound. This could explain why coadministration of probenecid has little effect on the drug level in plasma. Trough values were systematically below 5 ng/ml with all the regimens. This indicates that oral administration of 100 to 200 mg of TIBO once daily rarely leads to levels in plasma that are above 20 to 40 ng/ml, which represents the 90% inhibitory concentration of TIBO against HIV-1 in MT-4 cells. Thus, oral therapy may require a much higher dosage and/or frequent daily administration to achieve HIV-1 inhibition in vivo. The study did not aim to evaluate the efficacy of TIBO in this small group of patients with very poor prognoses. However, interestingly, one patient had a significant drop of p24 antigen level while under intravenous therapy and a subsequent rise under oral therapy. The heterogeneity of biological response we observed is in accordance with previous observations among AIDS and AIDS-related complex patients (5). Our study also confirms that tolerance of TIBO is excellent, but tolerability of oral administration of higher doses merits further evaluation. TIBO derivatives are promising agents which show very potent activity against HIV-1 in vitro. However, it appears that in their present formulation, oral administration would not achieve effective levels in plasma. Improvement of oral bioavailability is clearly needed before further studies to

PHARMACOKINETICS OF TIBO IN AIDS PATIENTS

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evaluate long-term efficacy and tolerability of these compounds are implemented. Moreover, rapid emergence of HIV-1 resistance has been shown with TIBO and other nonnucleoside reverse transcriptase inhibitors and will probably constitute a major obstacle for the future development of these molecules. ACKNOWLEDGMENT This study was supported by a grant from Janssen Research Foundation, Beerse, Belgium.

REFERENCES 1. Nunberg, J. H., W. A. Schleif, E. J. Boots, J. A. O'Brien, J. C. Quintero, J. M. Hoffman, E. A. Emini, and M. E. Goldman. 1991. Viral resistance to human immunodeficiency virus type 1-specific pyridinone reverse transcriptase inhibitors. J. Virol. 65:48874892. 2. Pauwels, R., K. Andries, Z. Debyser, M. J. Kulda, D. Schols, H. J. Breslin, R. Woestenborghs, J. Desmyter, M. A. C. Janssen, E. De Clercq, and P. A. J. Janssen. New TIBO derivatives are potent inhibitors of HIV-1 replication and are synergistic with 2',3'-dideoxynucleoside analogs. Submitted for publication. 3. Pauwels, R., K Andries, J. Desmyter, et al. 1990. Potent and selective inhibition of HIV-1 replication in vitro by a novel series of tetrahydroimidazo[4,5,1-jk][1,4]-benzodiazepin-2(1H)-one and -thione (TIBO) derivatives, p. 103-122. In E. De Clercq (ed.), Design of anti-AIDS drugs. Elsevier Biomedical Press, Amsterdam. 4. Pauwels, R., K. Andries, J. Desmyter, et al. 1990. Potent and selective inhibition of HIV-1 replication in vitro by a novel series of TIBO derivatives. Nature (London) 343:470-474. 5. Pialoux, G., M. Youle, B. Dupont, B. Gazzard, G. F. M. J. Cauwenbergh, P. A. M. Stoffels, S. Davies, J. De Saint Martin, and P. A. J. Janssen. 1991. Pharmacokinetics of R 82913 in patients with AIDS or AIDS-related complex. Lancet 338:140143. 6. Richman, D., C. K Shih, J. Rose, J. Grfflin, I. Lowy, S. Goff, and P. Prodanovich. 1991. Human immunodeficiency virus type 1 mutants resistant to nonnucleoside inhibitors of reverse transcriptase arise in tissue culture. Proc. Natl. Acad. Sci. 88:1124111245. 7. Yarchoan, R., J. M. Pluda, C. F. Perno, H. Mitsuya, and S. Broder. 1991. Anti-retroviral therapy of human immunodeficiency virus infection: current strategies and challenges for the future. Blood 78:859-884.