Partial Responses and Stable Disease Achieved with Bispecific as a Single-Agent Safety and Target Engagement Established for Anti-RSPO3 REDWOOD CITY, Calif., Nov. 29, 2016 (GLOBE NEWSWIRE) -- OncoMed Pharmaceuticals Inc. (NASDAQ:OMED) presented initial first-in-human data from its ongoing Phase 1 clinical trials of anti-DLL4/VEGF bispecific (OMP-305B83) and anti-RSPO3 (OMP-131R10) antibodies in two posters at the 28th EORTC-NCI-AACR Molecular Targets and Cancer Therapeutics Symposium being held in Munich, Germany. "In these first-in-human Phase 1 trials of our anti-DLL4/VEGF bispecific and anti-RSPO3 antibodies we have accomplished the primary goal of defining the safety profiles and establishing the single-agent doses for these agents. We have also observed initial evidence of anti-tumor activity in patients treated to date," said Jakob Dupont, M.D., Chief Medical Officer of OncoMed. "Dual blockade of DLL4 and VEGF has shown synergies preclinically, and in the clinic we are seeing evidence of single-agent activity with partial responses in ovarian and uterine cancers and stable disease in about one-third of the Phase 1 patients treated. We look forward to completing these trials and, in the near future, initiating Phase 1b studies with the anti-DLL4/VEGF bispecific in combination with standard of care in ovarian and colorectal cancers." Dr. Dupont continued, "Data from the ongoing anti-RSPO3 Phase 1a/b trial show evidence of target engagement and some encouraging signals of prolonged stable disease. With a single-agent dose identified and a good understanding of the safety profile of anti-RSPO3, we are excited to continue enrolling the biomarker-selected and combination portions of this study. Overexpression of RSPO3 is associated with the growth of a number of solid tumors, including colorectal cancers, and we have developed a CLIA-validated assay and a custom liquid biopsy to identify tumors with RSPO3 high gene expression and gene fusions where responses to treatment may be more likely." Anti-DLL4/VEGF Bispecific - Interim Phase 1a Data in Advanced Solid Tumors As of the data cut off of October 17, 2016, a total of 51 patients with advanced solid tumors had received single-agent doses ranging from 0.5 to 12.5 mg/kg every three weeks in the ongoing Phase 1a clinical trial of OncoMed's anti-DLL4/VEGF bispecific antibody. Safety and Pharmacokinetics: Anti-DLL4/VEGF bispecific was generally well tolerated with hypertension, headache, fatigue and pulmonary hypertension being the most common drug-related toxicities. One dose-limiting toxicity of diverticulitis occurred at 2.5 mg/kg. Hypertension side effects were successfully managed with anti-hypertensives and most pulmonary hypertension adverse events were reversible and of mild to moderate severity. A dose of 7.5 mg/kg once every three weeks was set for the Phase 1a expansion cohort following the observation of Grade 3 and 4 toxicities at the 10 mg/kg dose. The anti-DLL4/VEGF bispecific had a half-life of 14 days and anti-drug antibody response occurred primarily at low doses (=3.5 mg/kg). Efficacy: Two of the 46 patients (4%) evaluable for anti-tumor effects had unconfirmed partial responses, while another sixteen (35%) patients achieved stable disease. The partial responses occurred in patients with ovarian cancer and uterine carcinosarcoma. Five of eight evaluable ovarian patients had reductions in tumor volume and remained on therapy for 129, 170, 185, 309 and 323 days as of the data cut off. Data from the ongoing Phase 1a trial of the anti-DLL4/VEGF bispecific were presented in a poster titled, " A first-in-man Phase 1a study of the bispecific anti-DLL4/anti-VEGF antibody OMP-305B83 in patients with previously treated solid tumors "(Poster #P057; Abstract #87) by Dr. Kathleen Moore of the Stephenson Oklahoma Cancer Center at the University of Oklahoma. Anti-RSPO3 - Interim Phase 1a/b Data in Advanced Solid Tumors and Colorectal Cancer As of the data cut-off date of October 11, 2016, 23 patients in the anti-RSPO3 Phase 1a/b clinical trial were evaluable for safety and 15 patients were evaluable for anti-tumor activity. Interim safety, response, pharmacokinetics and biomarker data were included in the analyses in this ongoing clinical trial. Safety and Pharmacokinetics: Anti-RSPO3 was generally well tolerated as a single agent with the most common adverse events being fatigue and nausea in sixteen subjects treated at doses ranging from 2.5 to 15 mg/kg every two weeks. No dose-limiting toxicities were observed. Based on evidence of target engagement observed by changes in serum biomarkers, a single-agent dose of 15.0 mg/kg every two weeks was selected. Anti-RSPO3 has an estimated half-life of 13 days. Among seven safety-evaluable Phase 1b colorectal cancer patients who received anti-RSPO3 in combination with FOLFIRI (folinic acid, fluorouracil and irinotecan) chemotherapy the combination did not appear to exacerbate the toxicities of either drug. Dose-escalation continues in the combination portion of the trial.