Protara Therapeutics has touted a 66% complete response (CR) rate for its cell therapy among certain bladder cancer patients as “impressive,” despite this rate halving at the 12-month mark.
The New York-based biotech has been evaluating TARA-002—a cell therapy designed to activate immune cells within the tumor and generate a pro-inflammatory response—in the phase 2 open-label Advanced-2 trial of patients with high-risk non-muscle invasive bladder cancer (NMIBC). The participants either haven’t received or were unresponsive to Bacillus Calmette-Guérin (BCG), an immunotherapy used as the standard of care in the indication.
Among BCG-unresponsive patients, the latest interim analysis showed that 15 out of 22 (68.2%) of evaluable patients had experienced CR as of Jan. 28. However, this rate had dropped to five of 15 patients (33.3%) among patients who had reached 12 months of treatment.
Raj Satkunasivam, M.D., the study’s investigator, described the 12-month data as “maturing” while showing “promising signals of durability,” in the company’s Feb. 24 release.
“These clinically meaningful response rates and favorable tolerability profile make TARA-002 a potentially promising treatment option,” added Satkunasivam, who is a urologic oncologist and associate professor at Houston Methodist Hospital.
The data were more consistent among the BCG-naïve cohort, where the CR was 66.7% (18 out of 27 patients) at six months and 57.9% (11 of 19) at 12 months. Protara will share the data at the American Society of Clinical Oncology Genitourinary Cancers Symposium in San Francisco on Friday.
When it came to tolerability, the majority of treatment-related adverse events (TRAEs) were grade 1 and transient, Protara noted. There with no TRAEs graded 3 or above, and no patients discontinued treatment due to TRAEs, the company added.
But investors appeared unsure about the latest readout, sending Protara’s stock down 12% in premarket trading Tuesday to $6.50 from a Monday closing price of $7.43.
This morning’s market reaction was a far cry from December 2024, when the biotech saw its share price double on the back of earlier data from the same study that suggested a 72% six-month CR across BCG exposures. This included an 100% CR rate at six months among four evaluable BCG-unresponsive patients, who Protara said at the time are designed to be a registrational cohort and align with FDA draft guidance for the specific patient population.
Still, Protara CEO Jesse Shefferman said the data generated from the trial to date “highlight TARA-002’s potential as a meaningful addition to the treatment landscape.”
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“In addition to demonstrating impressive efficacy and safety, TARA-002 overcomes the limitations of existing NMIBC treatments that burden patients as well as urologists and their practices,” Shefferman added.
“We look forward to continuing to advance TARA-002’s clinical development as we work to bring this treatment to patients,” the CEO added.
The company has now reached its target enrollment of 31 patients who haven’t received BCG therapy and is continuing to enroll patients who were unresponsive to that treatment. The biotech said it remains on track to launch another study specifically in BCG-naïve patients in the second half of the year.
NMIBC makes up about 80% of bladder cancer cases, with about 65,000 Americans diagnosed with the form of bladder cancer every year. Merck & Co.’s blockbuster PD-1 inhibitor Keytruda is already approved to treat patients with BCG-unresponsive NMIBC, while Pfizer and AstraZeneca are hoping their own PD-1 drugs sasanlimab and Imfinzi, respectively, will also gain the FDA nod.
