Proteolix Initiates Phase 1b Clinical Trial of Carfilzomib

Patient dosing has commenced in a Phase 1b clinical trial to evaluate the safety and efficacy of Proteolix's lead anti-cancer agent, carfilzomib (PR-171), in combination with lenalidomide and dexamethasone in patients with relapsed multiple myeloma. Carfilzomib selectively blocks proteasome activity, causing apoptosis in cancer cells. In single agent Phase 1 studies carfilzomib has demonstrated encouraging anti-tumor activity and has been generally well tolerated.

The Phase 1b clinical trial is designed to evaluate safety and to establish a maximum-tolerated dose of carfilzomib in combination with lenalidomide and dexamethasone on a twenty-eight day treatment cycle. Lenalidomide in combination with dexamethasone is indicated for use in patients with multiple myeloma who have had at least one prior therapy. Patients will be divided into four cohorts and will receive escalating doses of carfilzomib and lenalidomide, combined with a set dose of dexamethasone. A secondary endpoint for the trial is overall response rate at four months.

"Carfilzomib has been generally well-tolerated in patients and we believe that the product's selectivity and potency provide a solid rationale for use in combination with existing treatment protocols," said Lori Kunkel, M.D., Proteolix's Chief Medical Officer. "Initiating our first combination trial of carfilzomib complements our multi-pronged strategy to thoroughly explore carfilzomib's potential in the treatment of patients with multiple myeloma for whom treatment options may be limited."

In addition to the Phase 1b clinical trial announced today, Proteolix is currently evaluating carfilzomib as a single agent for the treatment of multiple myeloma in two Phase 2 clinical trials.

A Phase 2 clinical trial of single-agent carfilzomib in patients with relapsed and refractory multiple myeloma recently began enrolling its second cohort of approximately 40 patients to explore safety, tolerability and activity using a higher dose schedule. This trial is being conducted in collaboration with the Multiple Myeloma Research Consortium (MMRC) and is designed to evaluate patients' overall response rate after four cycles of carfilzomib. All patients enrolled in the trial have received prior treatment(s) with bortezomib and either lenalidomide or thalidomide and are refractory to their last treatment.

A second open-label, multi-center Phase 2 trial of single-agent carfilzomib in relapsed multiple myeloma patients is also currently enrolling patients. The goal of this study is to evaluate carfilzomib's activity based on a patient's prior treatment with bortezomib. The company plans to present interim data from both of these Phase 2 trials by year end. A complete list of Proteolix's ongoing clinical trials of carfilzomib may be found at http://www.clinicaltrials.gov.

About Carfilzomib

Carfilzomib is a structurally- and mechanistically-novel proteasome inhibitor that exhibits a high level of selectivity for a single active site in the proteasome with minimal cross reactivity to other protease classes.