Safety and Tolerability of Conatumumab in Combination with Bortezomib or Vorinostat in Patients with Relapsed or Refractory Lymphoma.

Abstract 1708

Poster Board I-734

Conatumumab is an investigational, fully human, monoclonal antibody agonist of human death receptor 5 (DR5 [TRAIL receptor 2]) that activates caspases and triggers apoptosis in sensitive tumor cells. DR5 is expressed by a variety of lymphoma cell lines, and TRAIL receptor agonists have been shown to induce apoptosis in lymphoma cells and lymphoma xenografts. Bortezomib and vorinostat are active and approved agents in certain lymphoma subtypes. In addition, they enhance death receptor-mediated apoptosis in multiple tumor models. In this 2-part study, we evaluated conatumumab in combination with bortezomib or vorinostat to treat patients (pts) with relapsed or refractory lymphoma. The dose-escalation phase evaluated the safety and tolerability of escalating doses of conatumumab in combination with bortezomib or vorinostat; the dose-expansion phase was designed to estimate the efficacy of conatumumab plus bortezomib in pts with mantle cell lymphoma (MCL). Here we present data from the dose-escalation phase. Eligibility criteria included: relapsed or refractory low-grade lymphoma, mantle cell lymphoma (MCL), diffuse large cell lymphoma, or Hodgkin lymphoma; age ≥ 18 years; informed consent; ECOG performance status of 0 or 1; life expectancy of > 3 months; adequate organ function; no prior treatment with bortezomib or vorinostat; no evidence of CNS involvement by lymphoma; and no primary CNS lymphoma. Three to 6 pts were enrolled into 1 of 3 sequential dose cohorts (1.5, 5, or 15 mg/kg) of conatumumab administered intravenously every 3 weeks (on day 1 of every 21-day cycle) in combination with either bortezomib (1.3 mg/m² IV twice weekly for 2 weeks followed by a 10-day rest period) or vorinostat (400 mg orally daily). Endpoints included safety, maximum tolerated dose (MTD) of conatumumab, pharmacokinetics (PK) of conatumumab, incidence of anti-conatumumab antibodies, and best tumor response (complete response [CR] and partial response [PR]). CRs were confirmed by FDG-PET and bone marrow biopsy per Cheson criteria (2007). Monocyte DR5 occupancy by conatumumab was determined as an exploratory endpoint. As of July 9, 2009, 27 pts were enrolled and 23 received ≥1 dose of conatumumab: 3, 3, and 6 pts at 1.5, 5, and 15 mg/kg conatumumab + bortezomib; 7, 3, and 1 pt at 1.5, 5, and 15 mg/kg conatumumab + vorinostat. 15 pts were men; median (range) age was 53 (23 to 81) years; ECOG PS 0 = 65%, 1 = 26%, unknown = 9%; disease stage I = 4%, II = 4%, III = 39%, IV = 48%, unknown = 4%. Nine pts are still receiving treatment. The most common treatment-emergent adverse events (AE) were: fatigue (13 pts), diarrhea (9 pts), constipation (8 pts), nausea (8 pts), thrombocytopenia (8 pts), headache (7 pts), anemia (5 pts), dizziness (5 pts), and peripheral neuropathy (5 pts). A total of 6 and 3 pts reported worst grade 3 and 4 AEs, respectively, with no apparent differences between the 2 drug combinations. There were 2 DLTs: grade 3 prolonged Qt at 1.5 mg/kg conatumumab + vorinostat and grade 4 pulmonary embolism at 15 mg/kg conatumumab + bortezomib. An MTD has not been reached. Anti-conatumumb antibodies have not been detected in any pt. After one dose of conatumumab at 1.5, 5, or 15 mg/kg after bortezomib or vorinostat, conatumumab exposures were slightly higher (< 2-fold) than those in the first-in-human monotherapy study, indicating minimal effect of bortezomib or vorinostat on PK of conatumumab. Two pts had a confirmed CR: 1 pt with diffuse large cell lymphoma (1.5 mg/kg vorinostat cohort) at day 97 and 1 pt with nodular sclerosis Hodgkin lymphoma (5 mg/kg vorinostat cohort) at day 169. Thirteen pts had stable disease as their best objective response, 10 of whom had tumor shrinkage (range [based on sum of nodal and extra-nodal at each visit], -1.74% to -68.24%]). Receptor occupancy data will be presented. The combination of conatumumab with either bortezomib or vorinostat did not result in an unacceptable rate of dose-limiting toxicities and showed preliminary evidence of anti-tumor activity in pts with relapsed or refractory lymphoma. The expansion phase in pts with MCL treated with conatumumab plus bortezomib is currently enrolling.