ASCO 12. PD-1 Immunotherapy Makes a Splash at ASCO

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1 PD-1 Immunotherapy Makes a Splash at ASCO By Gregory R. Wolfe, PhD Epigenetic variation and genetic instability in tumor cells yield a variety of tumor antigens that the immune system can recognize to distinguish tumor cells from normal cells. These antigens are shed by tumors and are collected by antigen presenting cells (APC). An immune response is initiated when APCs present tumor antigens to T-cells; a second ligand localized on APCs serves as a co-regulatory signal that can either activate or suppress T-cell responses. This combination of signals modulates the amplitude of ensuing immune responses. With an activating signal, T-cells proliferate, migrate throughout the body to find their target, and lyse tumor cells. While it is evident that lymphocytes infiltrate growing tumors, tumorinfiltrating lymphocytes typically fail to generate a robust anticancer response. Furthermore, immune checkpoints are inhibitory pathways of the immune system that modulate magnitude and duration of T-cell responses. Immune checkpoints are critical for physiological homeostasis, including maintenance of self-tolerance and protection of tissues from damage as the immune system responds to pathogenic infection. However, these checkpoints may also serve as crucial regulators of immune escape in cancer. Checkpoint pathways are regulated by ligand/receptor interactions, and thus, may be targeted by blocking monoclonal antibodies. Theoretically, utilization of an antibody to prevent interactions of ligands with checkpoint receptors should release the brake on the immune system to enhance a response against cancer. The clinical and commercial feasibility of an immune checkpoint blocking agent has been demonstrated recently with the launch of ipilimumab [Yervoy: Bristol-Myers Squibb], a human cytotoxic T-lymphocyte antigen 4 (CTLA-4)-blocking antibody. It is the first cancer immunotherapeutic agent of this class to gain regulatory approval. CTLA4 is a negative regulator of T-cell activation. Ipilimumab binds to CTLA-4 and blocks the interaction of CTLA-4 with its ligands, CD80/ CD86. It has been demonstrated that CTLA-4 blockade augments T-cell activation and proliferation. The mechanism of action of ipilimumab s effect in patients with melanoma is indirect, possibly through T-cell mediated antitumor immune responses. Phase 3 clinical trials clearly demonstrated that ipilimumab improved overall survival in previously treated patients with unresectable or metastatic melanoma. In fact, the data were so strong that in 14 ONCOLOGY BUSINESS REVIEW ONCBIZ.COM JULY 2012

2 are able to suppress immune response by co-opting distinct immune checkpoints. Upon activation, T-cells express the PD-1 (programmed death-1) immune checkpoint receptor on their surface. Binding of PD-1 to its ligand, either PD-ligand 1 (PD-L1) or PD-L2, inhibits immune response and leads to T-cell anergy and death. Typical function of the PD-1 inhibitory pathway is to downregulate immune response when appropriate and thus prevent destruction of normal tissues. However, PD-L1 is frequently expressed on the surface of tumor cells, and suppression of the antitumor immune response occurs when PD-1 on activated T-cells encounters PD-L1 expressed on the tumor cell surface. Several reports suggest that up-regulation of PD-L1 in tumors correlates with suppressed T-cell activation and poor prognosis. 2 This suggests that PD-1 may be a viable target for anticancer treatment; in fact, a number of antibodies directed against PD-1 or its ligands, designed to block the interaction of PD-1 with PD-L1, are now in early stages of development (Table 1). Impressive Clinical Results from Blockade of the PD-1 Immune Checkpoint Pathway One of the hottest topics at this year s American Society of Clinical Oncology s (ASCO) annual meeting was the role of PD-1 in suppression of antitumor immunity. Impressive results from a large Phase 1 study of a fully human anti-pd-1 IgG4 monoclonal antibody [BMS ; Bristol-Myers Squibb/Ono Pharmaceuticals] were presented. 3-6 Patients (n=296) with advanced melanoma, renal cell carcinoma (RCC), non-small cell lung cancer (NSCLC), colorectal cancer (CRC) or castrate-resistant prostate cancer (CRPC) with progressive disease after one to five systemic 16 ONCOLOGY BUSINESS REVIEW ONCBIZ.COM JULY 2012 Preliminary data suggest that PD-L1 expression in pretreatment tumor biopsies correlates with clinical outcome. therapies were treated with BMS The maximum tolerated dose (MTD) was not identified, and expansion cohorts were enrolled at 10 mg/kg in all tumor types. Just 15 patients of 296 (5%) discontinued treatment due to drug-related adverse events (AEs). The most common AEs (all grades) were fatigue (24%), rash (12%), and diarrhea (11%). Grade 3/4 toxicities occurred in 14% of patients, and three deaths were attributed to pneumonitis (2 NSCLC, 1 CRC), a toxicity that has been previously observed with other immunotherapies. At the time of presentation, 236 patients were evaluable for response, and clinical activity was observed in three of the five tumor types evaluated. Encouraging objective response rates (ORR) and clinical benefit rates (ORR + stable disease), respectively, were reported in patients with melanoma (28%, 34%), NSCLC (18%, 25%) including squamous and nonsquamous histologies, and RCC (27%, 54%). Responses were durable, with approximately two-thirds lasting at least one year. The NSCLC data are particularly noteworthy as these tumors typically do not respond to immunotherapy, and the enrolled patients were heavily pretreated (55% had received three or more prior lines). Preliminary data suggest that PD-L1 expression in pretreatment tumor biopsies correlates with clinical outcome. Sixteen of 25 patients whose tumors expressed PD-L1 responded to therapy, while none of the 17 patients whose tumors did not express PD-L1 responded. Preliminary results from the ongoing, first-inhuman, Phase 1 study (CA ) of BMS , a fully human anti-pd-l1 IgG4 monoclonal antibody, were reported by Tykodi. 7 Patients with advanced and

3 progressive melanoma, NSCLC, RCC, CRC, ovarian, pancreatic, breast or gastric cancers received BMS The MTD was not identified at doses up to 10 mg/kg, and no correlation between AEs and drug dose was observed. Patient accrual is ongoing, but 207 were evaluable for safety, of whom just 12 patients (6%) discontinued treatment due to drug-related AEs. Common AEs (any grade) included fatigue (16%), infusion-related reaction (10%), and diarrhea (9%). Grade 3/4 AEs occurred in 9% of patients and, as of this analysis, no drug-related deaths were observed. Response data were available for 160 patients, and ORRs were reported for patients with melanoma (17%), NSCLC (10%) including responders with squamous and non-squamous histologies, RCC (12%), and ovarian cancer (6%). Rates of progressionfree survival (PFS) at six months were as follows: melanoma (42%), NSCLC (31%), RCC (53%) and ovarian (22%). Durable tumor regressions and prolonged disease stabilization ( 6 months) were reported for a proportion of patients with NSCLC (some longer than 1 year), melanoma (some nearly 2 years) and RCC. Results were also presented from a single-institution, Phase 1, dose-escalation study designed to evaluate safety and activity of a humanized anti- PD-1 IgG4 monoclonal antibody [MK-3475; Merck & Co]. 8 In part A of this study, patients with solid tumors were assigned to one of three dose cohorts followed by a part B expansion cohort in melanoma patients. Seventeen patients were evaluable from part A: NSCLC (n=5); melanoma (n=3); colorectal (n=3); carcinoid/neuroendocrine (n=2), and other (n=4). The most frequent drug-related AEs were pruritus, fatigue, and nausea; drug-related pneumonitis developed in one patient. No Grade 3 or higher AEs were observed. In part A of this study, confirmed, durable, partial responses (PRs) were achieved in two of three melanoma patients, including one with a BRAF mutation and one without. The third melanoma patient achieved stable disease as best response. An unconfirmed PR was also achieved in a NSCLC patient with squamous cell histology. Preliminary activity (according to immune-related Response Criteria) from the first 10 patients in part B was also presented: two melanoma patients (20%) achieved unconfirmed PRs and five (50%) achieved stable disease (SD) as their best response. There were four responders according to RECIST criteria. Conclusion These studies demonstrate the potential of targeting the PD-1/PD-L1 checkpoint pathway as a therapeutic strategy across multiple tumor histologies. PD-1 checkpoint blocking agents appear to be very well tolerated and have efficacy in many advanced tumor types. Although these results are preliminary, they suggest that these PD-1 inhibitors may be more efficacious and less toxic than other checkpoint inhibitors, such as ipilimumab in metastatic melanoma, prompting Dr. Antonio Ribas to state in his presentation, PD-1/PD-L1 inhibitors are likely the most impacting new agents in metastatic melanoma. Preliminary results suggest that PD-L1 expression in tumor tissue may serve as a biomarker for selection of patients for PD-1 checkpoint blocking therapy, although larger studies are required to confirm these JULY 2012 ONCBIZ.COM ONCOLOGY BUSINESS REVIEW 17

4 observations. Many questions remain unanswered about this novel approach to targeting cancer. Is efficacy limited to tumors that express PD-L1? How durable are responses? Can these agents be utilized in combination with other therapies to improve efficacy? How do these agents compare to CTLA4 inhibitors? This is only the beginning of the road for this class of agents, and many of these questions may be answered in the near future as additional studies are completed and those being developed by numerous other pharmaceutical companies. In fact, BMS is planning registrational trials for BMS in metastatic melanoma, NSCLC and RCC, which will begin at the end of 2012 and early ASCO 2012 was PD-1 s debutant ball, but we may be only a few years away from its coronation. GRW References: 1. Hodi FS, O Day SJ, McDermott DF, et al. Improved survival with ipilimumab in patients with metastatic melanoma. N Engl J Med. 2010;363: Pardoll DM. The blockade of immune checkpoints in cancer immunotherapy. Nat Rev Cancer. 2012;12: Topalian SL, Brahmer JR, Hodi FS, et al. Anti-PD-1 (BMS , MDX-1106) in patients with advanced solid tumors: Clinical activity, safety, and a potential biomarker for response. J Clin Oncol. 2012;30: Abstract CRA Brahmer JR, Horn L, Antonia S, et al. Clinical activity and safety of anti-pd1 (BMS , MDX-1106) in patients with advanced non-small-cell lung cancer (NSCLC). J Clin Oncol. 2012;30: Abstract Hodi FS, Sznol M, McDermott DF, et al. Clinical activity and safety of anti-pd-1 (BMS , MDX-1106) in patients with advanced melanoma (MEL). J Clin Oncol. 2012;30: Abstract McDermott DF, Drake CG., Sznol M, et al. Clinical activity and safety of anti-pd-1 (BMS , MDX-1106) in patients with previously treated metastatic renal cell carcinoma (mrcc). J Clin Oncol. 2012;30: Abstract Tykodi SS, Brahmer JR, Hwu W-J, et al. PD-1/PD-L1 pathway as a target for cancer immunotherapy: Safety and clinical activity of BMS , an anti-pd-l1 antibody, in patients with solid tumors. J Clin Oncol. 2012;30: Abstract Patnaik A, Kang SP, Tolcher AW, et al. Phase I study of MK-3475 (anti-pd-1 monoclonal antibody) in patients with advanced solid tumors. J Clin Oncol. 2012;30: Abstract About Kantar Health Kantar Health is a global, evidencebased decision support partner to the world s leading pharmaceutical, biotech, device and diagnostic companies. Our 700+ staff act as catalysts, working closely with customers to drive distinctive decision-making that help them prioritize product development and portfolios, differentiate their brands and ensure product profitability after launch. We are unique in that we bring together clinical, medical and methodological expertise, commercial/marketing know-how and proprietary data. It is this rare combination, together with our unparalleled stakeholder reach, that enable us to mobilize incisive, imaginative and timely ROI-driven solutions, empowering clients to deliver better healthcare options to their customers. Kantar Health s oncology-related offers include Oncology Conference Insight, client-directed oncology conference coverage that analyzes the most important research at significant oncology meetings; and CancerMPact Treatment Architecture, which assesses the current clinical management of cancer patients by site and stage for all treatment modalities. If you would like us to act as catalysts for you, contact us at >>OBR DAILY NEWS FLASHES Doctors said that the frequency of cancer drug shortages has begun to decline at an ASCO press conference held during the June annual meeting. (Wall Street Journal/Health blog, 6/4/12) A government panel recommended that healthy men skip a widely used screening test for prostate cancer, saying the harm outweighed the benefits for all age groups. (Boston Globe, 5/21/12) Notable personalized therapies in the pipeline highlighted at 2012 ASCO included GlaxoSmithKline s BRAF inhibitors trametinib and dabrafenib [advanced melanoma] and Boehringer Ingelheim s EGFR inhibitor afatinib [non-small cell lung cancer]. (New York Times, 6/4/12) 18 ONCOLOGY BUSINESS REVIEW ONCBIZ.COM JULY 2012

5 The catalyst for successful decision making in the life sciences industry What s of greatest interest to you at this year s major oncology meetings? Every year, Kantar Health sends multidisciplinary teams of oncology experts to significant oncology meetings to attend and analyze the most important clinical presentations, satellite symposia, poster sessions, and floor exhibits. Click here to learn more. We are a global, evidence-based decision support partner to the world s leading pharmaceutical, biotech, device and diagnostic companies. For more information on Kantar Health s CancerMPact, an invaluable oncology decision-support tool for the U.S., Western Europe, Japan and China, click here to learn more. If you would like us to act as catalysts for you, contact us at