Shares of Allogene Therapeutics Inc. (NASDAQ:ALLO) leapt 36% higher to $42.12 on Thursday after limited data from a small number of relapsed/refractory (r/r) non-Hodgkin lymphoma patients showed a combination of the company's anti-CD19 allogeneic CAR T candidate, ALLO-501, and an anti-CD52 monoclonal antibody, ALLO-647, met with an overall response rate of 78%. There were three complete responses (CRs) and four partial responses. Allogene is developing '501 with Les Laboratoires Servier SAS under an exclusive license granted by Paris-based Cellectis SA.
While much of the focus landed on efficacy Thursday, the trial's primary endpoint is the proportion of patients experiencing dose-limiting toxicities at increasing doses of ALLO-501. No dose-limiting toxicities or graft-vs.-host disease were observed so far, Allogene said.
News of the interim data arrived amid a flood of new results to be presented at the upcoming online-only American Society of Clinical Oncology annual meeting, an event than last year drew about 42,500 registrants from around the world to Chicago.
Admitting "low expectations" of such an early trial at first, Jefferies analyst Biren Amin said he now sees Allogene as "one of the winners" of the conference, which is expected to offer additional color on the study's progress during the meeting's scientific program. It's slated to be presented by Sattva Neelapu, a professor in the department of lymphoma/myeloma at The University of Texas MD Anderson Cancer Center.
"While 80% of patients actually respond to CAR T-cell therapy, only about 40% stay in remission long term. So, there is room to improve its effectiveness," Neelapu said in January, commenting on the field as part of an MD Anderson publication. He also noted challenges around the safety and cost of CAR T therapies, the former of which is a focus of the phase I study.
As of the January 2020 data cutoff for the ASCO abstract describing the Allogene study, with a median follow-up of 2.7 months, investigators saw four patients in ongoing response and three patients having progressed at two, four and six months. Looking forward to additional color on the cell doses for the three progressed patients, Biren said his team would hypothesize that they were on the lowest dose. "We also want to see if the CRs have made it out to three months," he said.
J.P. Morgan analyst Cory Kasimov was a little more circumspect, noting that "in our view, this is good initial data but is hard to interpret relative to other CAR T/CD19 approaches given the limited details in the abstract."
The drugs are being tested in a single-arm, open-label phase I study called Alpha. It's enrolling adults with relapsed or refractory large B-cell lymphoma or follicular lymphoma after a lymphodepletion regimen comprising fludarabine, cyclophosphamide and ALLO-647. The study, which has a target enrollment of 54 participants, is intended to evaluate safety, efficacy, cell kinetics and immunogenicity.
South San Francisco-based Allogene plans to use data on ALLO-501 to accelerate development of a second-generation version of ALLO-501, known as ALLO-501A, from which it has removed rituximab recognition domains. Researchers expect that change will potentially facilitate treatment of more patients, since rituximab is a typical part of a treatment regimen for a patient with NHL, it said. A potentially pivotal phase I/II trial of ALLO-501A, called Alpha2, is expected to start this quarter, subject to completion of manufacturing of the product.