OncoMed Pharmaceuticals Inc. announced that the first patient has been enrolled and dosed in the Phase 1b portion of the Phase 1a/1b clinical trial of anti-RSPO3 (OMP-131R10). The Phase 1b portion of the trial will assess the safety, pharmacokinetics, pharmacodynamics and initial evidence of efficacy of anti-RSPO3 in combination with the chemotherapeutic standard of care in metastatic colon cancer, known as FOLFIRI (folinic acid, fluorouracil and irinotecan) in colorectal cancer patients who have received one prior treatment. The company's ongoing Phase 1a/1b clinical trial is initially enrolling patients with advanced refractory solid tumors to assess the safety, pharmacokinetics, pharmacodynamics and initial evidence of efficacy of the anti-RSPO3 antibody.

Enrollment commenced on the single-agent portion of the anti-RSPO3 first-in-human clinical trial in July 2015. Now that several dose cohorts have been safely cleared the decision has been made by OncoMed and the investigators of the trial to initiate the combination phase of the study. Dose escalation of the single agent portion of the study continues in parallel.

Once a single-agent dose has been identified, biomarker-selected patients will be enrolled in a Phase 1a expansion arm to evaluate possible anti-tumor activity. The trial is being conducted at five sites in the United States.