Immatics' solid tumor data fan PRAME flame, sending stock soaring

Immatics has posted more evidence that PRAME may live up to its billing as “one of the most promising and most prevalent” solid tumor targets. In updated phase 1b data, the biotech reported a 64% response rate and early signs that its T-cell therapy may have deep and durable effects against cancer cells. 

Transatlantic biotech Immatics has steadily built up excitement about its work on PRAME across a series of data drops. The initial interest was tempered by early relapses—and durability remains an outstanding question—but, with each update, the biotech has chipped away at doubts about a target that has caught the eye of biotechs including Immunocore, BioNTech and Adaptimmune. 

The latest update covers 11 heavily pre-treated, last-line patients who received the T-cell receptor (TCR) therapy IMA203. Seven patients had partial responses after six weeks. Immatics confirmed six of those responses at the three-month scan. The seventh responder is yet to have a three-month scan. 

Importantly, five of the seven responses are ongoing. After a median follow-up of 8.5 months, Immatics is yet to reach the median duration of response. Two of the responses are still going more than nine months after treatment. Investors responded to the data by driving Immatics’ share price up 27% to over $9 in after-hours trading, and analysts at Mizuho Securities are increasingly optimistic about the asset. 

“The data came as a surprise to us, in terms of its timing, and more importantly, its quality,” the analysts wrote in a note to investors. “The data provide us confidence in the quality of additional individual cohort updates for IMA203 that may come, and more importantly, a more extensive update on the program expected later this year.”

Mizuho analysts see the update planned for the fourth quarter as “a data event which we believe has potential to serve as a meaningful point of value inflection.” With each positive update, Immatics both validates its decision to focus on PRAME, the target of the cell therapy IMA203 and its preclinical TCR bispecific, and offers encouragement to other companies with programs aimed at the antigen.

Immunocore has made PRAME a focal point of its pipeline and is scheduled to publish phase 1/2 data in the first half of next year. BioNTech paid Medigene $29 million for a preclinical PRAME cell therapy early this year. And Adaptimmune, having been dumped by GSK, has a preclinical asset in its pipeline. 

Immatics plans to start a “registration-directed” phase 2 trial of IMA203 in the first half of next year. With PRAME highly prevalent in a range of tumor types, and IMA203 triggering responses in patients with cutaneous and uveal melanoma, synovial sarcoma, head and neck cancer and ovarian cancer, the midphase study could serve as a launchpad for an attack on a long list of indications.