Faculty Bibliography

The immunotherapeutic agent ipilimumab has helped address a significant unmet need in the treatment of advanced melanoma. Ipilimumab is a fully human monoclonal antibody that targets cytotoxic T-lymphocyte antigen-4 (CTLA-4), thereby augmenting antitumor immune responses. After decades in which a number of clinical trials were conducted, ipilimumab was the first therapy to improve overall survival in a randomized, controlled phase III trial of patients with advanced melanoma. These results led to the regulatory approval of ipilimumab at 3 mg/kg for the treatment of unresectable or metastatic melanoma. More than 17,000 patients worldwide have received ipilimumab, either as a commercial drug at 3 mg/kg or in clinical trials and expanded access programs at different doses. Consistent with its proposed mechanism of action, the most common toxicities associated with ipilimumab therapy are inflammatory in nature. These immune-related adverse events were mostly reversible when effective treatment guidelines were followed. Importantly, long-term follow-up of patients who received ipilimumab in a phase III trial showed that 24% survived at least two years, and in phase II studies, a proportion of patients survived at least five years. Evaluation of ipilimumab is ongoing in the adjuvant setting for melanoma, and for advanced disease in nonsmall cell lung, small cell lung, prostate, ovarian, and gastric cancers.

PURPOSE To assess pharmacodynamic effects and intrinsic and acquired resistance mechanisms of the BRAF inhibitor vemurafenib in BRAF(V600)-mutant melanoma, leading to an understanding of the mechanism of action of vemurafenib and ultimately to optimization of metastatic melanoma therapy. METHODS In the phase II clinical study NP22657 (BRIM-2), patients received oral doses of vemurafenib (960 mg twice per day). Serial biopsies were collected to study changes in mitogen-activated protein kinase (MAPK) signaling, cell-cycle progression, and factors causing intrinsic or acquired resistance by immunohistochemistry, DNA sequencing, or somatic mutation profiling. Results Vemurafenib inhibited MAPK signaling and cell-cycle progression. An association between the decrease in extracellular signal-related kinase (ERK) phosphorylation and objective response was observed in paired biopsies (n = 22; P = .013). Low expression of phosphatase and tensin homolog showed a modest association with lower response. Baseline mutations in MEK1(P124) coexisting with BRAF(V600) were noted in seven of 92 samples; their presence did not preclude objective tumor responses. Acquired resistance to vemurafenib associated with reactivation of MAPK signaling as observed by elevated ERK1/2 phosphorylation levels in progressive lesions and the appearance of secondary NRAS(Q61) mutations or MEK1(Q56P) or MEK1(E203K) mutations. These two activating MEK1 mutations had not previously been observed in vivo in biopsies of progressive melanoma tumors. CONCLUSION Vemurafenib inhibits tumor proliferation and oncogenic BRAF signaling through the MAPK pathway. Acquired resistance results primarily from MAPK reactivation driven by the appearance of secondary mutations in NRAS and MEK1 in subsets of patients. The data suggest that inhibition downstream of BRAF should help to overcome acquired resistance.

We describe a randomized three-arm phase I study of ipilimumab administered alone (I group) or in combination with dacarbazine (D group) or carboplatin/paclitaxel (CP group) in patients with previously untreated advanced melanoma. The primary objective was to estimate the effect of ipilimumab on the pharmacokinetics (PK) of dacarbazine and paclitaxel and, conversely, to estimate the effects of dacarbazine and carboplatin/paclitaxel on the PK of ipilimumab. Secondary objectives included evaluation of the safety and anti-tumor activity of ipilimumab when administered alone or with either dacarbazine or carboplatin/paclitaxel, and assessment of pharmacodynamic (PD) effects of ipilimumab on the immune system when administered alone or with either of the two chemotherapies. Ipilimumab was administered at a dose of 10 mg/kg intravenously (IV) every 3 weeks for up to 4 doses. Patients in the D group received dacarbazine 850 mg/m(2) IV every 3 weeks. Patients in the CP group received paclitaxel 175 mg/m(2) IV and carboplatin [AUC=6] IV every 3 weeks. Starting at week 24, patients without dose-limiting toxicities were eligible to receive maintenance ipilimumab at 10 mg/kg every 12 weeks until disease progressed or toxicity required discontinuation. Of 59 randomized patients, 18 (30.5%) discontinued treatment due to adverse events. Response rates by modified WHO criteria were 29.4% (I group), 27.8% (D group), and 11.1% (CP group). No major PK or PD interactions were observed when ipilimumab was administered with dacarbazine or with the carboplatin/paclitaxel combination. This study demonstrated that ipilimumab can be combined safely with two chemotherapy regimens commonly used in advanced melanoma.

BACKGROUND: Approximately 50% of melanomas harbor activating (V600) mutations in the serine-threonine protein kinase B-RAF (BRAF). The oral BRAF inhibitor vemurafenib (PLX4032) frequently produced tumor regressions in patients with BRAF V600-mutant metastatic melanoma in a phase 1 trial and improved overall survival in a phase 3 trial. METHODS: We designed a multicenter phase 2 trial of vemurafenib in patients with previously treated BRAF V600-mutant metastatic melanoma to investigate the efficacy of vemurafenib with respect to overall response rate (percentage of treated patients with a tumor response), duration of response, and overall survival. The primary end point was the overall response rate as ascertained by the independent review committee; overall survival was a secondary end point. RESULTS: A total of 132 patients had a median follow-up of 12.9 months (range, 0.6 to 20.1). The confirmed overall response rate was 53% (95% confidence interval [CI], 44 to 62; 6% with a complete response and 47% with a partial response), the median duration of response was 6.7 months (95% CI, 5.6 to 8.6), and the median progression-free survival was 6.8 months (95% CI, 5.6 to 8.1). Primary progression was observed in only 14% of patients. Some patients had a response after receiving vemurafenib for more than 6 months. The median overall survival was 15.9 months (95% CI, 11.6 to 18.3). The most common adverse events were grade 1 or 2 arthralgia, rash, photosensitivity, fatigue, and alopecia. Cutaneous squamous-cell carcinomas (the majority, keratoacanthoma type) were diagnosed in 26% of patients. CONCLUSIONS: Vemurafenib induces clinical responses in more than half of patients with previously treated BRAF V600-mutant metastatic melanoma. In this study with a long follow-up, the median overall survival was approximately 16 months. (Funded by Hoffmann-La Roche; ClinicalTrials.gov number, NCT00949702.).

BACKGROUND: Ipilimumab monotherapy (at a dose of 3 mg per kilogram of body weight), as compared with glycoprotein 100, improved overall survival in a phase 3 study involving patients with previously treated metastatic melanoma. We conducted a phase 3 study of ipilimumab (10 mg per kilogram) plus dacarbazine in patients with previously untreated metastatic melanoma. METHODS: We randomly assigned 502 patients with previously untreated metastatic melanoma, in a 1:1 ratio, to ipilimumab (10 mg per kilogram) plus dacarbazine (850 mg per square meter of body-surface area) or dacarbazine (850 mg per square meter) plus placebo, given at weeks 1, 4, 7, and 10, followed by dacarbazine alone every 3 weeks through week 22. Patients with stable disease or an objective response and no dose-limiting toxic effects received ipilimumab or placebo every 12 weeks thereafter as maintenance therapy. The primary end point was overall survival. RESULTS: Overall survival was significantly longer in the group receiving ipilimumab plus dacarbazine than in the group receiving dacarbazine plus placebo (11.2 months vs. 9.1 months, with higher survival rates in the ipilimumab-dacarbazine group at 1 year (47.3% vs. 36.3%), 2 years (28.5% vs. 17.9%), and 3 years (20.8% vs. 12.2%) (hazard ratio for death, 0.72; P<0.001). Grade 3 or 4 adverse events occurred in 56.3% of patients treated with ipilimumab plus dacarbazine, as compared with 27.5% treated with dacarbazine and placebo (P<0.001). No drug-related deaths or gastrointestinal perforations occurred in the ipilimumab-dacarbazine group. CONCLUSIONS: Ipilimumab (at a dose of 10 mg per kilogram) in combination with dacarbazine, as compared with dacarbazine plus placebo, improved overall survival in patients with previously untreated metastatic melanoma. The types of adverse events were consistent with those seen in prior studies of ipilimumab; however, the rates of elevated liver-function values were higher and the rates of gastrointestinal events were lower than expected on the basis of prior studies. (Funded by Bristol-Myers Squibb; ClinicalTrials.gov number, NCT00324155.).

OBJECTIVE: Ipilimumab is a fully human, anti-cytotoxic T-lymphocyte antigen-4 (CTLA-4) monoclonal antibody that has demonstrated antitumor activity in advanced melanoma. We evaluated the safety and efficacy of ipilimumab alone and in combination with dacarbazine (DTIC) in patients with unresectable, metastatic melanoma. METHODS: Chemotherapy-naive patients were randomized in this multicenter, phase II study to receive ipilimumab at 3 mg/kg every 4 weeks for four doses either alone or with up to six 5-day courses of DTIC at 250 mg/m(2)/day. The primary efficacy endpoint was objective response rate. RESULTS: Seventy-two patients were treated per-protocol (ipilimumab plus DTIC, n = 35; ipilimumab, n = 37). The objective response rate was 14.3% (95% CI, 4.8-30.3) with ipilimumab plus DTIC and was 5.4% (95% CI, 0.7-18.2) with ipilimumab alone. At a median follow-up of 20.9 and 16.4 months for ipilimumab plus DTIC (n = 32) and ipilimumab alone (n = 32), respectively, median overall survival was 14.3 months (95% CI, 10.2-18.8) and 11.4 months (95% CI, 6.1-15.6); 12-month, 24-month, and 36-month survival rates were 62%, 24% and 20% for the ipilimumab plus DTIC group and were 45%, 21% and 9% for the ipilimumab alone group, respectively. Immune-related adverse events were, in general, medically manageable and occurred in 65.7% of patients in the combination group versus 53.8% in the monotherapy group, with 17.1% and 7.7% >/=grade 3, respectively. CONCLUSION: Ipilimumab therapy resulted in clinically meaningful responses in advanced melanoma patients, and the results support further investigations of ipilimumab in combination with DTIC

Ipilimumab is a fully human, monoclonal antibody that blocks cytotoxic T-lymphocyte antigen-4 to potentiate an antitumor T-cell response. This agent improved overall survival in a phase III trial in previously treated patients with advanced melanoma. Because the mechanism of action for ipilimumab is thought to be HLA independent, most trials enrolled patients without regard to HLA subtype. However, enrollment in the phase III trial was restricted to class-I HLA-A*0201-positive patients because two of the three arms contained an HLA-A*0201-restricted gp100 vaccine. HLA typing was also performed prospectively in several phase II trials and was available for 93.5% of patients. In this retrospective analysis, pooled efficacy and safety data are presented according to HLA-A*0201 status and dose from pretreated patients randomized to 0.3, 3, or 10 mg/kg ipilimumab in four phase II trials. Median overall survival (OS) was similar for the 187 HLA-A*0201-positive [9.3 months, 95% CI (confidence interval) 7.4-11.5] and 266 HLA-A*0201-negative patients [11.4 months, 95% CI 9.3-15.1] randomized to ipilimumab at all doses across the four phase II trials. These data are comparable to the OS for the 137 HLA-A*0201-positive patients randomized to ipilimumab in the phase III study [10.1 months, 95% CI 8.0-13.8]. Ipilimumab-induced adverse events and immune-related adverse events (skin, gastrointestinal, hepatic, other) also occurred at similar frequencies among patients in the phase II and III trials, regardless of HLA-A*0201 status. These findings support the hypothesis that ipilimumab-treated patients with advanced melanoma have similar outcomes regardless of their HLA-A*0201 status.

BACKGROUND: An improvement in overall survival among patients with metastatic melanoma has been an elusive goal. In this phase 3 study, ipilimumab--which blocks cytotoxic T-lymphocyte-associated antigen 4 to potentiate an antitumor T-cell response--administered with or without a glycoprotein 100 (gp100) peptide vaccine was compared with gp100 alone in patients with previously treated metastatic melanoma. METHODS: A total of 676 HLA-A*0201-positive patients with unresectable stage III or IV melanoma, whose disease had progressed while they were receiving therapy for metastatic disease, were randomly assigned, in a 3:1:1 ratio, to receive ipilimumab plus gp100 (403 patients), ipilimumab alone (137), or gp100 alone (136). Ipilimumab, at a dose of 3 mg per kilogram of body weight, was administered with or without gp100 every 3 weeks for up to four treatments (induction). Eligible patients could receive reinduction therapy. The primary end point was overall survival. RESULTS: The median overall survival was 10.0 months among patients receiving ipilimumab plus gp100, as compared with 6.4 months among patients receiving gp100 alone (hazard ratio for death, 0.68; P<0.001). The median overall survival with ipilimumab alone was 10.1 months (hazard ratio for death in the comparison with gp100 alone, 0.66; P=0.003). No difference in overall survival was detected between the ipilimumab groups (hazard ratio with ipilimumab plus gp100, 1.04; P=0.76). Grade 3 or 4 immune-related adverse events occurred in 10 to 15% of patients treated with ipilimumab and in 3% treated with gp100 alone. There were 14 deaths related to the study drugs (2.1%), and 7 were associated with immune-related adverse events. CONCLUSIONS: Ipilimumab, with or without a gp100 peptide vaccine, as compared with gp100 alone, improved overall survival in patients with previously treated metastatic melanoma. Adverse events can be severe, long-lasting, or both, but most are reversible with appropriate treatment. (Funded by Medarex and Bristol-Myers Squibb; ClinicalTrials.gov number, NCT00094653.)

During the past decade, new insights into the mechanisms by which T-cell activation and proliferation are regulated have led to the identification of checkpoint proteins that either up- or down-modulate T-cell reactivity. In the presence of active malignancy, pathophysiologic inhibition of T-cell activity may predominate over stimulation. A number of antibodies have been generated that can block inhibitory checkpoint proteins or promote the activity of activating molecules. In murine models, their use alone or with a vaccine strategy has resulted in regression of poorly immunogenic tumors and cures of established tumors. The prototypical immune regulatory antibodies are those directed against cytotoxic T-lymphocyte antigen-4, a molecule present on activated T cells. In this review, the preclinical rationale and clinical experience with 2 anticytotoxic T-lymphocyte antigen-4 antibodies are extensively discussed, demonstrating that abrogation of an immune inhibitory molecule can result in significant regression of tumors and long-lasting responses. The unique kinetics of antitumor response and the characteristic immune-related side effects of ipilimumab are also discussed. This clinical efficacy of this promising antitumor agent has been evaluated in 2 randomized phase III trials, whose results are eagerly awaited. Programmed death (PD)-1 is another immune inhibitory molecule against which an abrogating human antibody has been prepared. Initial preclinical testing with anti-PD-1 and anti-PD-L1 has shown encouraging results. Stimulatory molecules such as CD40, 41-BB, and OX-40 are also targets for antibody binding and activation, not blockade, and early dose ranging trials with antibodies against all 3 have shown that they can mediate regression of tumors, albeit with their own spectrum of side effects that are different from those that occur with abrogation of immune inhibition.