Elad Sharon

PD-1 Blockade with Pembrolizumab in Advanced Merkel-Cell Carcinoma

BACKGROUND Merkel-cell carcinoma is an aggressive skin cancer that is linked to exposure to ultraviolet light and the Merkel-cell polyomavirus (MCPyV). Advanced Merkel-cell carcinoma often responds to chemotherapy, but responses are transient. Blocking the programmed death 1 (PD-1) immune inhibitory pathway is of interest, because these tumors often express PD-L1, and MCPyV-specific T cells express PD-1. METHODS In this multicenter, phase 2, noncontrolled study, we assigned adults with advanced Merkel-cell carcinoma who had received no previous systemic therapy to receive pembrolizumab (anti-PD-1) at a dose of 2 mg per kilogram of body weight every 3 weeks. The primary end point was the objective response rate according to Response Evaluation Criteria in Solid Tumors, version 1.1. Efficacy was correlated with tumor viral status, as assessed by serologic and immunohistochemical testing. RESULTS A total of 26 patients received at least one dose of pembrolizumab. The objective response rate among the 25 patients with at least one evaluation during treatment was 56% (95% confidence interval [CI], 35 to 76); 4 patients had a complete response, and 10 had a partial response. With a median follow-up of 33 weeks (range, 7 to 53), relapses occurred in 2 of the 14 patients who had had a response (14%). The response duration ranged from at least 2.2 months to at least 9.7 months. The rate of progression-free survival at 6 months was 67% (95% CI, 49 to 86). A total of 17 of the 26 patients (65%) had virus-positive tumors. The response rate was 62% among patients with MCPyV-positive tumors (10 of 16 patients) and 44% among those with virus-negative tumors (4 of 9 patients). Drug-related grade 3 or 4 adverse events occurred in 15% of the patients. CONCLUSIONS In this study, first-line therapy with pembrolizumab in patients with advanced Merkel-cell carcinoma was associated with an objective response rate of 56%. Responses were observed in patients with virus-positive tumors and those with virus-negative tumors. (Funded by the National Cancer Institute and Merck; ClinicalTrials.gov number, NCT02267603.).

Major Cancer Regressions in Mesothelioma After Treatment with an Anti-Mesothelin Immunotoxin and Immune Suppression

In patients with advanced chemotherapy-refractory mesothelioma, treatment with the anti-mesothelin immunotoxin SS1P and immunosuppression with pentostatin and cyclophosphamide resulted in marked and durable tumor regressions. Combating Mesothelioma by Suppressing Friendly Fire Immunotoxins, which combine a bacterial toxin with an antibody fragment that recognizes a specific protein, offer a way to selectively target and kill cancer cells. Unfortunately, the patient’s immune system usually attacks the immunotoxin as a foreign protein, destroying it before it can reach its target and deliver the toxin to the tumor. Now, Hassan and coauthors have demonstrated a combination treatment approach for preventing the formation of antitoxin antibodies in mesothelioma patients. Mesothelioma is an aggressive tumor of the pleural and peritoneal membranes, which normally has a poor prognosis and very limited treatment options. SS1P is an immunotoxin targeting mesothelin, a protein that is only found in the mesothelial membranes and highly expressed in mesothelioma. In past clinical trials, the vast majority of treated patients developed antibodies against SS1P after only one cycle of treatment, precluding its continued use as a therapeutic agent. To overcome this problem, Hassan et al. treated chemotherapy-resistant mesothelioma patients with pentostatin and cyclophosphamide, chemotherapeutic agents that specifically deplete lymphocytes and can therefore prevent the formation of antitoxin antibodies, before giving SS1P to the patients. This treatment combination greatly delayed antibody formation, allowing the patients to receive multiple cycles of SS1P, which resulted in improved clinical outcomes. Future work will be needed to further prolong the presence of this immunotoxin because most patients in the current trial eventually developed antibodies against SS1P. Additional work will also be necessary to clarify the mechanism of the combination treatment and determine whether the immunomodulatory drugs contribute any direct antitumor effects. Nevertheless, the results presented by Hassan and coauthors provide a promising approach for treating an aggressive and deadly tumor, and demonstrate a clever way to overcome immune rejection of immunotoxin treatment. Immunotoxins are potent anticancer agents with an unusual mechanism of action: inhibition of protein synthesis resulting in apoptotic cell death. Immunotoxins have produced many durable complete responses in refractory hairy cell leukemia, where patients rarely form antibodies to the bacterial toxin component of the immunotoxin. Patients with mesothelioma, however, have normal immune systems and form antibodies after one cycle, and tumor responses to the immunotoxin have not been observed in this disease. We describe the results of a trial in which major antitumor responses were seen in patients with advanced mesothelioma who received the anti-mesothelin immunotoxin SS1P, together with pentostatin and cyclophosphamide, to deplete T and B cells. Of 10 patients with chemotherapy-refractory mesothelioma, 3 have had major tumor regressions with 2 ongoing at 15 months, and 2 others responded to chemotherapy after discontinuing immunotoxin therapy. Antibody formation was markedly delayed, allowing more SS1P cycles to be given, but this alone does not appear to account for the marked antitumor activity observed.

Phase I Clinical Trial of the Chimeric Anti-Mesothelin Monoclonal Antibody MORAb-009 in Patients with Mesothelin Expressing Cancers

Purpose: MORAb-009 is a chimeric monoclonal antibody that targets mesothelin, a tumor differentiation antigen overexpressed in pancreatic cancer, ovarian cancer, mesothelioma, and other malignancies. We conducted a phase I clinical trial of MORAb-009 in patients with advanced mesothelin-expressing cancers to determine its safety, dose-limiting toxicity (DLT), and maximum tolerated dose (MTD). Methods: Cohorts consisting of 3 to 6 subjects each received MORAb-009 intravenously on days 1, 8, 15, and 22 at progressively increasing doses ranging from 12.5 to 400 mg/m2. Disease evaluation with computed tomography occurred on day 35. Subjects with responding or stable disease could receive additional cycles of MORAb-009. Results: A total of 24 subjects were treated including 13 mesothelioma, 7 pancreatic cancer, and 4 ovarian cancer patients. The median number of MORAb-009 infusions was 4 (range 1–24 infusions). At the 400 mg/m2 dose level, 2 subjects experienced DLT (grade 4 transaminitis and a grade 3 serum sickness). Thus, although there were other contributing causes of these adverse events, 200 mg/m2 was considered the MTD. Other adverse events at least possibly related to MORAb-009 included 7 drug hypersensitivity events (all grade 1 or 2) and a thromboembolic event (grade 4). Eleven subjects had stable disease. There was a dose-dependent increase in serum MORAb-009 concentration. Conclusion: MORAb-009 is well tolerated and the MTD when administered weekly is conservatively set at 200 mg/m2. In this group of previously treated patients, 11 subjects had stable disease. Phase II studies of MORAb-009 in different mesothelin-expressing cancers are ongoing.

Phase 1 study of the antimesothelin immunotoxin SS1P in combination with pemetrexed and cisplatin for front-line therapy of pleural mesothelioma and correlation of tumor response with serum mesothelin, megakaryocyte potentiating factor, and cancer antigen 125

The primary objective of this study was to determine the safety and maximum tolerated dose (MTD) of the antimesothelin immunotoxin SS1(dsFv)PE38 (SS1P) (a recombinant antimesothelin immunotoxin consisting of a murine antimesothelin variable antibody fragment [Fv] linked to PE38, a truncated portion of Pseudomonas exotoxin A) in combination with pemetrexed and cisplatin in chemotherapy‐naive patients with advanced malignant pleural mesothelioma (MPM). Secondary objectives included tumor response, SS1P pharmacokinetics, and serum biomarkers of response.

Mesothelin-targeted agents in clinical trials and in preclinical development.

Mesothelin is a tumor differentiation antigen that is highly expressed in several malignant diseases in humans, including malignant mesothelioma and pancreatic, ovarian, and lung adenocarcinomas. The limited expression of mesothelin on normal human tissues and its high expression in many common cancers make it an attractive candidate for cancer therapy. Several agents, including an immunotoxin, monoclonal antibody, antibody drug conjugate, and tumor vaccine, are in various stages of development to treat patients with mesothelin-expressing tumors. This review highlights ongoing clinical trials, as well as other approaches to exploit mesothelin for cancer therapy, that are in preclinical development. Mol Cancer Ther; 11(3); 517–25. ©2012 AACR.

Chemotherapy and targeted therapies for unresectable malignant mesothelioma.

The global burden of mesothelioma is expected to increase in the coming decades. As a result the development of more effective therapies with an emphasis on personalized treatments based on validated prognostic and predictive biomarkers is an essential requirement. Progress has been made in the last decade with the development of newer generation anti-folates leading to the current standard of care of pemetrexed and cisplatin in patients with unresectable disease. However, the median overall survival of patients with this combination treatment is only 12 months. There is no consensus regarding second line therapy for patients who have progressed or not responded to pemetrexed based therapies although gemcitabine in combination with a platinum compound or single agent vinorelbine is a reasonable option. The development of effective targeted agents that are active in mesothelioma has to date been disappointing. Strategies involving the addition of bevacizumab to pemetrexed and cisplatin in the frontline setting, the histone deacetylase inhibitor vorinostat as second line therapy and studies evaluating the utility of maintenance therapy in mesothelioma are all ongoing and appear promising. In addition clinical trials investigating immunotherapy and gene therapy in combination with chemotherapy could potentially improve the prognosis of patients with mesothelioma.

Sustained response of carcinoma ex pleomorphic adenoma treated with trastuzumab and capecitabine

BackgroundCarcinoma ex pleomorphic adenoma is a rare histologic subtype of salivary gland cancer with an overall poor prognosis. Limited histopathologic analyses have shown that some such tumors exhibit significant HER2/neu immunoreactivity, suggesting a potential role for HER2-based therapy. We report here a case of a 58-year old man with metastatic carcinoma ex pleomorphic adenoma who achieved a sustained long term response to combination therapy with trastuzumab and capecitabine.Case presentationA 58 year old man presented with T1N2bM0 carcinoma ex pleomorphic adenoma and underwent surgery followed by adjuvant radiation therapy. Multiple metastases to bone were documented one year later. Since the original tumor was strongly HER2/neu positive by immunohistochemistry, the patient was treated with trastuzumab, capecitabine, and zoledronic acid. He experienced total resolution of symptoms and repeat FDG-PET scan after three cycles revealed interval disease resolution. Continued treatment has resulted in maintenance of disease control for over 2 years.ConclusionThis case illustrates the successful long term treatment of carcinoma ex pleomorphic adenoma with targeted therapy with trastuzumab in combination with chemotherapy. In the absence of definitive clinical trials which are unlikely to be performed due to the rarity of this tumor, case reports such as this one suggest potential utility for trastuzumab in combination with chemotherapy in the treatment of HER2/neu-overexpressing carcinoma ex pleomorphic adenoma.

Pentostatin plus cyclophosphamide safely and effectively prevents immunotoxin immunogenicity in murine hosts.

Purpose: The success of immunotoxin therapy of cancer is limited by host production of neutralizing antibodies, which are directed toward the Pseudomonas exotoxin A (PE) component. In this proof-of-principle study using a well-established murine model, we hypothesized that a newly developed immune depletion regimen consisting of pentostatin plus cyclophosphamide would abrogate anti-immunotoxin reactivity. Experimental Design: BALB/c hosts were injected weekly with recombinant immunotoxin (RIT) SS1P, which is an antimesothelin Fv antibody fragment genetically fused to a 38 kDa portion of PE, and has been evaluated in clinical trials. Experimental cohorts received induction chemotherapy consisting of pentostatin (P) plus cyclophosphamide (C) prior to initial RIT exposure; some cohorts received further maintenance PC therapy of varying intensity just prior to each weekly RIT challenge. Cohorts were monitored for T, B, myeloid cell depletion, and for total anti-SS1P antibody (Ab) formation. Results: Controls uniformly developed anti-SS1P Ab after the third RIT exposure. Induction PC therapy reduced the frequency of hosts with anti-SS1P Ab. Abrogation of antibody generation was improved by maintenance PC therapy: nearly 100% of recipients of intensive PC maintenance were free of anti-SS1P Ab after 9 weekly RIT doses. The most effective PC regimen yielded the greatest degree of host B-cell depletion, moderate T-cell depletion, and minimal myeloid cell depletion. Conclusions: Induction and maintenance PC chemotherapy safely prevented anti-immunotoxin antibody formation with uniform efficacy. These data suggest that immunotoxin therapy might be used in combination with pentostatin plus cyclophosphamide chemotherapy to improve the targeted therapy of cancer. Clin Cancer Res; 17(11); 3697–705. ©2011 AACR.

Can an Immune Checkpoint Inhibitor (Sometimes) Make Things Worse

Champiat and colleagues suggest that a small subset of patients at their center treated with PD1/PDL1 inhibitors appear to exhibit hyperprogression of disease. This commentary goes over some limitations in their preliminary analysis, a possible mechanism to explain the phenomenon, and a means by which other investigators can attempt to validate and further characterize these results. Clin Cancer Res; 23(8); 1879–81. ©2017 AACR. See related article by Champiat et al., p. 1920

Immuno-oncology trial endpoints: Capturing clinically meaningful activity

Immuno-oncology (I-O) has required a shift in the established paradigm of toxicity and response assessment in clinical research. The design and interpretation of cancer clinical trials has been primarily driven by conventional toxicity and efficacy patterns observed with chemotherapy and targeted agents, which are insufficient to fully inform clinical trial design and guide therapeutic decisions in I-O. Responses to immune-targeted agents follow nonlinear dose–response and dose–toxicity kinetics mandating the development of novel response evaluation criteria. Biomarker-driven surrogate endpoints may better capture the mechanism of action and biological response to I-O agents and could be incorporated prospectively in early-phase I-O clinical trials. While overall survival remains the gold standard for evaluation of clinical efficacy of I-O agents in late-phase clinical trials, exploration of potential novel surrogate endpoints such as objective response rate and milestone survival is to be encouraged. Patient-reported outcomes should also be assessed to help redefine endpoints for I-O clinical trials and drive more efficient drug development. This paper discusses endpoints used in I-O trials to date and potential optimal endpoints for future early- and late-phase clinical development of I-O therapies. Clin Cancer Res; 23(17); 4959–69. ©2017 AACR. See all articles in this CCR Focus section, “Clinical Trial Design Considerations in the Immuno-oncology Era.”