NEWS
npg
But the multiplicity of PD-L1 immunohistochemistry assays, and their cost, are alarming oncologists and pathologists. Few institutions will invest in all the necessary equipment, they say. And each test uses a different antibody clone and different PD-L1 positivity cutoffs, which is likely to lead to confusion among users (Table 1). Opinions differ as to whether it’s enough to test PD-L1 expression on tumor cells or whether immune cells must also be stained. PD-L1 expression on macrophages infiltrating a lung cancer tumor. And few data have Arrows indicate macrophages (green; CD68) that express PD-L1 (red). been published on assay Cell nuclei are stained in blue. validation, and none on their comparative performance. toxicity. Why many PD-L1-negative patients Superficially, PD-L1 biology appears also respond remains unknown, but given straightforward. Cancer cells upregulate this observation, oncologists may not bother PD-L1, which binds the PD-1 receptor on with Keytruda and PD-L1 testing but instead tumor-reactive T cells, shutting them down give everyone Opdivo. “My off-protocol and creating an immunosuppressive environ- patients I would just start on Opdivo and ment in which tumors can thrive. Immune- give them a try, without the marker,” says checkpoint blockers restore T-cell activity David Carbone, an oncologist at Ohio State by targeting either the ligand PD-L1, as do University in Columbus. To the extent that Genentech’s atezolizumab and Medimmune’s others agree, “that’s a competitive disadvandurvalumab, or the PD-1 receptor, as with tage for [Keytruda],” he adds. Merck’s Keytruda and BMS’s Opdivo. Both Ben Creelan, an oncologist at the Moffitt approaches have worked well in the clinic. Cancer Center in Tampa, Florida, agrees Clinicians are now faced with a choice. that PD-L1 testing in relapsed lung cancer They can opt for Keytruda paired to its diag- patients is not a priority. Such patients, who nostic, or they can just order Opdivo, with or have endured highly toxic chemotherapy, without PD-L1 testing. “It depends on which are desperate for an alternative, he says. oncologist you ask,” says David Rimm, a “Whether the test is positive or negative, they pathologist at Yale University in New Haven, still want to shoot for it [immunotherapy],” Connecticut. But in Opdivo’s Checkmate-57 says Creelan. “I’m just happy to give it.” trial, even PD-L1-negative patients did as Companion diagnostics—and Keytruda— well on Opdivo as on docetaxel, with less are likely to take off if approved as first-line measures in lung cancer. About a dozen Table 1 Selected immune-checkpoint companion diagnostics in clinical phase 3 first-line trials are in progress for the development for NSCLC various agents, almost all of them selecting Diagnostic PD-L1 IHC Cutoff for PD-L1 Companion Combination patients using a PD-L1 status assay. “Those company assay positivity immunotherapy status studies are pretty much done, and probDako (Agilent) 22C3 PharmDx 50% of tumor cells Keytruda (pembrolizumab) Approved ably will report next year some time,” says Dako (Agilent) 28-8 PharmDx 1%, 5% or 10% of Opdivo Approved (as comCarbone. Assuming they’re positive, “that’ll tumor cells (nivolumab)(BMS) plementary assay) totally change the landscape.” It will also be In development Ventana (Roche) SP142 Highest threshold: 5% Atezolizumab (RG7155) when Dako starts making real money from of tumor cells, 50% of (Genentech/Roche) immune cells its two diagnostic tests. That is, if pathologists don’t use cheaper, Ventana (Roche) SP263 25% of tumor cells Durvalumab (MEDI4736) In development (Medimmune/Amgen) non-FDA-approved PD-L1 assays instead. The US Food and Drug Administration (FDA) on 2 October gave the go-ahead to the first pairing of a companion diagnostic with an immune-checkpoint inhibitor, for second-line treatment of metastatic non– small cell lung cancer (NSCLC). The therapy was Kenilworth, New Jersey–based Merck’s Keytruda (pembrolizumab) for patients with tumors expressing programed cell death ligand-1 (PD-L1) assayed with the monoclonal antibody 22C3 from Dako North America, an Agilent Technologies company. A week later the FDA approved a second, “complementary” PD-L1 diagnostic, with a different Dako antibody clone, as a stand-alone test to predict responses to New York–based Bristol-Myers Squibb’s (BMS) checkpoint inhibitor Opdivo (nivolumab) in metastatic NSCLC. The promise is that testing tumors for PD-L1 status will enable oncologists to precisely match therapy to patient. But the reality is that PD-L1 is an imperfect biomarker (Box 1), and a profusion of tests threatens to confuse pathologists and limit their practical options. Checkpoint inhibitors can be dramatically effective, and a test that qualifies patients for treatment on the basis of PD-L1 status may make sense. In Merck’s phase 1b Keynote-1 trial, lung cancer patients with more than 50% of tumor cells staining for PD-L1 had a 52% response rate, compared with a 16% response rate in the remaining patients. Such results have been remarkably consistent across trials, except for squamous NSCLC, where PD-L1 status makes no difference. More PD-L1 companion diagnostics are in the works. A rabbit monoclonal antiPD-L1 test from Ventana Medical Systems (a Roche company) in Tucson, Arizona, could be approved next year for use with S. San Francisco–based Genentech’s immune- checkpoint inhibitor atezolizumab, and Cambridge, UK–based MedImmune is also testing a Ventana companion diagnostic (Table 1).
NATURE BIOTECHNOLOGY VOLUME 33 NUMBER 12 DECEMBER 2015
Genentech
© 2015 Nature America, Inc. All rights reserved.
Predictive biomarkers for checkpoints, first tests approved
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NEWS
npg
© 2015 Nature America, Inc. All rights reserved.
Box 1 Fashioning the ideal biomarker Most talk of companion diagnostics for immunotherapies has, so far, been dominated by PD-L1. That could change. The ideal companion diagnostic, says oncologist Antoni Ribas at the University of California, Los Angeles, is one that captures other critical factors such as mutation load, tumor neoantigens (Science 348, 124–128, 2015) and the presence of CD8+ T cells at the tumor margin (Nature 516, 568–571, 2014). “PDL1 does not capture all of the biology we need to understand,” says Ribas, who has reported that expression of ten gamma-interferon response genes predicts melanoma patient response to Keytruda treatment (J. Clin. Oncol. 33, 2015 suppl. abstract 3001, 2015). Genentech, at the European Cancer Congress in Vienna, in September, also reported a gene signature predictive of the response to anti-PD-L1 antibody atezolizumab in metastatic non-small cell lung cancer. “A very, very striking association with overall survival, just looking at the T effector [cell] signature,” says Genentech’s Priti Hegde. Ideally, a signature would be combined with PD-L1 status, along with tumor immune cell detection and deep DNA sequencing for mutation load, says Ribas, who has cofounded a yet-to-be-funded startup, Arcteries, to sponsor prospective clinical trials. Genentech and other companies are testing their own biomarker combinations. An effective multiplex predictive biomarker may indicate monotherapy, a much cheaper and much less toxic option than immunotherapy combinations. “It makes no sense to me that the payers are OK to pay $300,000 for ipi-nivo [ipilimumab-nivolumab combination, approved by the FDA on 30 September] for two antibodies, and maybe even more to treat the toxicities, and not want to spend up front—I don’t know—four or five thousand [dollars], to do all of these,” says Ribas. “I think the biology will KG eventually win.”
“Even though both [Dako] tests have FDA They would have some way of standardizing approval… we’re about to incorporate a lab- PD-L1 m easurement and it would work with derived test, an LDT, which we’ve carefully multiple antibodies on multiple platforms.” characterized,” says Rimm. One reason is that But that, he notes, is not a good business the Dako immunohistochemistry tests must model: “They have a financial interest to only run on Dako’s Link 48 autostainer machine, produce a test they can protect.” Agilent, for which Yale’s lab would have to acquire. its part, says that it “will of course support “Another concern any initiatives which of ours is that the Public knowledge of these make life simpler Dako test for 22C3 companion diagnostics is for the pathologist.” is priced about ten Eventually one test scant because most of the times higher than may prevail in the most of the anti- data remain proprietary. marketplace. Priti bodies we use,” says Hegde, a senior sciRimm. Based on the standard insurance entist at Genentech overseeing immunotherimmunohistochemistry reimbursement apy biomarker programs, predicts that the code, “at that price we would actually lose best assay will eventually emerge from the money with every test.” Agilent won’t com- clinical trial data. “The diagnostic that shows ment on pricing, but in an e-mail to Nature the best association [with outcomes] should Biotechnology stated that LDT “home-brew be the one that will get the most acceptance,” test copies,” while useful for some purposes, she says. “The trials should speak for themlack the validation and company support to selves.” be reliable stand-alone predictive assays. Analytical accuracy also matters. The But even hospitals that choose to use the International Association for the Study of FDA-approved tests will probably not sup- Lung Cancer (IASLC) is conducting a study port more than one. “No laboratory is going comparing the analytical performance of to be willing” to do all the tests, says Rimm. all four companion diagnostics. (The two Ideally, says Rimm, the companies “would diagnostic companies and four pharmas make their platforms much more flexible. are collaborating.) The short-term goal is
1218
to compare the assays. Public knowledge of these companion diagnostics is scant because most of the data remain proprietary, says pathologist and IASLC CEO Fred Hirsch, who notes that analytical data on only one assay has been reported in a peer-reviewed journal. Hirsch, like Rimm, hopes eventually for “a harmonized assay which would apply to all four drugs,” but none is under development now. The different cutoff points for PD-L1 positivity (Table 1) add to the confusion. And Genentech’s Ventana assay alone stains for PD-L1 expression on immune cells in addition to tumor cells. “Our strong belief is that if you’re just looking at tumor cells, you’re missing patients who have high immune-cell expression of PD-L1 and who do derive benefit from these agents,” says Hegde. The antibodies’ biology could also lead to different results. “These immunohistochemistry antibodies recognize different epitopes of PD-L1, and so the results differ,” says Creelan. Dako’s two antibodies target the extracellular domain of PD-L1, whereas Ventana’s SP142 targets the cytoplasmic domain. Although the extracellular domain is the molecule’s functional ‘business end’, it may be cleaved off, leaving only the cytoplasmic domain to be detected. A similar situation affects the Her2 receptor and may account for the different results obtained in different Her2 assays. Many researchers also worry that tumor heterogeneity, changing PD-L1 expression over time, and pathologist inconsistency will confound routine testing. “With multiple tumors and multiple passes within a tumor, you can get different measurements,” said Yale oncologist Roy Herbst in May at the American Society for Clinical Oncology (ASCO) annual meeting. Says Carbone, “I have seen patients get re-biopsied, and be negative on the first and positive on the second.” But Rimm’s experiments show that heterogeneity, though present in tumors, varies little between tumor blocks, and he found a 95% concordance between pathologists when reading stains. “Pathologists can get it right,” he says. And Genentech recently reported a roughly 75% PD-L1 expression concordance between archival tumor tissue and new biopsies and re-sections. Genentech’s Hegde considers the problems overblown. “If it was really this bad none of us would see an association with outcomes,” she says. “BMS sees it, Merck sees it, we see it.” Ken Garber Ann Arbor, Michigan
VOLUME 33 NUMBER 12 DECEMBER 2015 NATURE BIOTECHNOLOGY
npg
But the multiplicity of PD-L1 immunohistochemistry assays, and their cost, are alarming oncologists and pathologists. Few institutions will invest in all the necessary equipment, they say. And each test uses a different antibody clone and different PD-L1 positivity cutoffs, which is likely to lead to confusion among users (Table 1). Opinions differ as to whether it’s enough to test PD-L1 expression on tumor cells or whether immune cells must also be stained. PD-L1 expression on macrophages infiltrating a lung cancer tumor. And few data have Arrows indicate macrophages (green; CD68) that express PD-L1 (red). been published on assay Cell nuclei are stained in blue. validation, and none on their comparative performance. toxicity. Why many PD-L1-negative patients Superficially, PD-L1 biology appears also respond remains unknown, but given straightforward. Cancer cells upregulate this observation, oncologists may not bother PD-L1, which binds the PD-1 receptor on with Keytruda and PD-L1 testing but instead tumor-reactive T cells, shutting them down give everyone Opdivo. “My off-protocol and creating an immunosuppressive environ- patients I would just start on Opdivo and ment in which tumors can thrive. Immune- give them a try, without the marker,” says checkpoint blockers restore T-cell activity David Carbone, an oncologist at Ohio State by targeting either the ligand PD-L1, as do University in Columbus. To the extent that Genentech’s atezolizumab and Medimmune’s others agree, “that’s a competitive disadvandurvalumab, or the PD-1 receptor, as with tage for [Keytruda],” he adds. Merck’s Keytruda and BMS’s Opdivo. Both Ben Creelan, an oncologist at the Moffitt approaches have worked well in the clinic. Cancer Center in Tampa, Florida, agrees Clinicians are now faced with a choice. that PD-L1 testing in relapsed lung cancer They can opt for Keytruda paired to its diag- patients is not a priority. Such patients, who nostic, or they can just order Opdivo, with or have endured highly toxic chemotherapy, without PD-L1 testing. “It depends on which are desperate for an alternative, he says. oncologist you ask,” says David Rimm, a “Whether the test is positive or negative, they pathologist at Yale University in New Haven, still want to shoot for it [immunotherapy],” Connecticut. But in Opdivo’s Checkmate-57 says Creelan. “I’m just happy to give it.” trial, even PD-L1-negative patients did as Companion diagnostics—and Keytruda— well on Opdivo as on docetaxel, with less are likely to take off if approved as first-line measures in lung cancer. About a dozen Table 1 Selected immune-checkpoint companion diagnostics in clinical phase 3 first-line trials are in progress for the development for NSCLC various agents, almost all of them selecting Diagnostic PD-L1 IHC Cutoff for PD-L1 Companion Combination patients using a PD-L1 status assay. “Those company assay positivity immunotherapy status studies are pretty much done, and probDako (Agilent) 22C3 PharmDx 50% of tumor cells Keytruda (pembrolizumab) Approved ably will report next year some time,” says Dako (Agilent) 28-8 PharmDx 1%, 5% or 10% of Opdivo Approved (as comCarbone. Assuming they’re positive, “that’ll tumor cells (nivolumab)(BMS) plementary assay) totally change the landscape.” It will also be In development Ventana (Roche) SP142 Highest threshold: 5% Atezolizumab (RG7155) when Dako starts making real money from of tumor cells, 50% of (Genentech/Roche) immune cells its two diagnostic tests. That is, if pathologists don’t use cheaper, Ventana (Roche) SP263 25% of tumor cells Durvalumab (MEDI4736) In development (Medimmune/Amgen) non-FDA-approved PD-L1 assays instead. The US Food and Drug Administration (FDA) on 2 October gave the go-ahead to the first pairing of a companion diagnostic with an immune-checkpoint inhibitor, for second-line treatment of metastatic non– small cell lung cancer (NSCLC). The therapy was Kenilworth, New Jersey–based Merck’s Keytruda (pembrolizumab) for patients with tumors expressing programed cell death ligand-1 (PD-L1) assayed with the monoclonal antibody 22C3 from Dako North America, an Agilent Technologies company. A week later the FDA approved a second, “complementary” PD-L1 diagnostic, with a different Dako antibody clone, as a stand-alone test to predict responses to New York–based Bristol-Myers Squibb’s (BMS) checkpoint inhibitor Opdivo (nivolumab) in metastatic NSCLC. The promise is that testing tumors for PD-L1 status will enable oncologists to precisely match therapy to patient. But the reality is that PD-L1 is an imperfect biomarker (Box 1), and a profusion of tests threatens to confuse pathologists and limit their practical options. Checkpoint inhibitors can be dramatically effective, and a test that qualifies patients for treatment on the basis of PD-L1 status may make sense. In Merck’s phase 1b Keynote-1 trial, lung cancer patients with more than 50% of tumor cells staining for PD-L1 had a 52% response rate, compared with a 16% response rate in the remaining patients. Such results have been remarkably consistent across trials, except for squamous NSCLC, where PD-L1 status makes no difference. More PD-L1 companion diagnostics are in the works. A rabbit monoclonal antiPD-L1 test from Ventana Medical Systems (a Roche company) in Tucson, Arizona, could be approved next year for use with S. San Francisco–based Genentech’s immune- checkpoint inhibitor atezolizumab, and Cambridge, UK–based MedImmune is also testing a Ventana companion diagnostic (Table 1).
NATURE BIOTECHNOLOGY VOLUME 33 NUMBER 12 DECEMBER 2015
Genentech
© 2015 Nature America, Inc. All rights reserved.
Predictive biomarkers for checkpoints, first tests approved
1217
NEWS
npg
© 2015 Nature America, Inc. All rights reserved.
Box 1 Fashioning the ideal biomarker Most talk of companion diagnostics for immunotherapies has, so far, been dominated by PD-L1. That could change. The ideal companion diagnostic, says oncologist Antoni Ribas at the University of California, Los Angeles, is one that captures other critical factors such as mutation load, tumor neoantigens (Science 348, 124–128, 2015) and the presence of CD8+ T cells at the tumor margin (Nature 516, 568–571, 2014). “PDL1 does not capture all of the biology we need to understand,” says Ribas, who has reported that expression of ten gamma-interferon response genes predicts melanoma patient response to Keytruda treatment (J. Clin. Oncol. 33, 2015 suppl. abstract 3001, 2015). Genentech, at the European Cancer Congress in Vienna, in September, also reported a gene signature predictive of the response to anti-PD-L1 antibody atezolizumab in metastatic non-small cell lung cancer. “A very, very striking association with overall survival, just looking at the T effector [cell] signature,” says Genentech’s Priti Hegde. Ideally, a signature would be combined with PD-L1 status, along with tumor immune cell detection and deep DNA sequencing for mutation load, says Ribas, who has cofounded a yet-to-be-funded startup, Arcteries, to sponsor prospective clinical trials. Genentech and other companies are testing their own biomarker combinations. An effective multiplex predictive biomarker may indicate monotherapy, a much cheaper and much less toxic option than immunotherapy combinations. “It makes no sense to me that the payers are OK to pay $300,000 for ipi-nivo [ipilimumab-nivolumab combination, approved by the FDA on 30 September] for two antibodies, and maybe even more to treat the toxicities, and not want to spend up front—I don’t know—four or five thousand [dollars], to do all of these,” says Ribas. “I think the biology will KG eventually win.”
“Even though both [Dako] tests have FDA They would have some way of standardizing approval… we’re about to incorporate a lab- PD-L1 m easurement and it would work with derived test, an LDT, which we’ve carefully multiple antibodies on multiple platforms.” characterized,” says Rimm. One reason is that But that, he notes, is not a good business the Dako immunohistochemistry tests must model: “They have a financial interest to only run on Dako’s Link 48 autostainer machine, produce a test they can protect.” Agilent, for which Yale’s lab would have to acquire. its part, says that it “will of course support “Another concern any initiatives which of ours is that the Public knowledge of these make life simpler Dako test for 22C3 companion diagnostics is for the pathologist.” is priced about ten Eventually one test scant because most of the times higher than may prevail in the most of the anti- data remain proprietary. marketplace. Priti bodies we use,” says Hegde, a senior sciRimm. Based on the standard insurance entist at Genentech overseeing immunotherimmunohistochemistry reimbursement apy biomarker programs, predicts that the code, “at that price we would actually lose best assay will eventually emerge from the money with every test.” Agilent won’t com- clinical trial data. “The diagnostic that shows ment on pricing, but in an e-mail to Nature the best association [with outcomes] should Biotechnology stated that LDT “home-brew be the one that will get the most acceptance,” test copies,” while useful for some purposes, she says. “The trials should speak for themlack the validation and company support to selves.” be reliable stand-alone predictive assays. Analytical accuracy also matters. The But even hospitals that choose to use the International Association for the Study of FDA-approved tests will probably not sup- Lung Cancer (IASLC) is conducting a study port more than one. “No laboratory is going comparing the analytical performance of to be willing” to do all the tests, says Rimm. all four companion diagnostics. (The two Ideally, says Rimm, the companies “would diagnostic companies and four pharmas make their platforms much more flexible. are collaborating.) The short-term goal is
1218
to compare the assays. Public knowledge of these companion diagnostics is scant because most of the data remain proprietary, says pathologist and IASLC CEO Fred Hirsch, who notes that analytical data on only one assay has been reported in a peer-reviewed journal. Hirsch, like Rimm, hopes eventually for “a harmonized assay which would apply to all four drugs,” but none is under development now. The different cutoff points for PD-L1 positivity (Table 1) add to the confusion. And Genentech’s Ventana assay alone stains for PD-L1 expression on immune cells in addition to tumor cells. “Our strong belief is that if you’re just looking at tumor cells, you’re missing patients who have high immune-cell expression of PD-L1 and who do derive benefit from these agents,” says Hegde. The antibodies’ biology could also lead to different results. “These immunohistochemistry antibodies recognize different epitopes of PD-L1, and so the results differ,” says Creelan. Dako’s two antibodies target the extracellular domain of PD-L1, whereas Ventana’s SP142 targets the cytoplasmic domain. Although the extracellular domain is the molecule’s functional ‘business end’, it may be cleaved off, leaving only the cytoplasmic domain to be detected. A similar situation affects the Her2 receptor and may account for the different results obtained in different Her2 assays. Many researchers also worry that tumor heterogeneity, changing PD-L1 expression over time, and pathologist inconsistency will confound routine testing. “With multiple tumors and multiple passes within a tumor, you can get different measurements,” said Yale oncologist Roy Herbst in May at the American Society for Clinical Oncology (ASCO) annual meeting. Says Carbone, “I have seen patients get re-biopsied, and be negative on the first and positive on the second.” But Rimm’s experiments show that heterogeneity, though present in tumors, varies little between tumor blocks, and he found a 95% concordance between pathologists when reading stains. “Pathologists can get it right,” he says. And Genentech recently reported a roughly 75% PD-L1 expression concordance between archival tumor tissue and new biopsies and re-sections. Genentech’s Hegde considers the problems overblown. “If it was really this bad none of us would see an association with outcomes,” she says. “BMS sees it, Merck sees it, we see it.” Ken Garber Ann Arbor, Michigan
VOLUME 33 NUMBER 12 DECEMBER 2015 NATURE BIOTECHNOLOGY
