Janux dives as gaps in prostate cancer study data worry investors

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Dec 2 (Reuters) – Shares of Janux Therapeutics slumped nearly 50% on Tuesday as investors reacted to limited disclosure in the company’s early-stage study update for its prostate cancer treatment.

The lead candidate, JANX007, is being developed to treat metastatic castration-resistant prostate cancer, a form that progresses despite the standard approach of maintaining very low testosterone levels.

The drug developer said patients who received the drug achieved up to nine months without their cancer worsening, and eight out of 27 evaluable patients saw their tumors shrink, according to updated interim data from the early-stage study reported late on Monday.

While analysts said the selloff was overdone, they noted that limited data disclosure and lack of clarity on key timelines could influence investor sentiment.

Shares of the drug developer were down 49.9% at $17.04, on track for its biggest single-day drop on record if losses hold.

The new release addresses key questions but “leaves several variables and gaps to be filled,” said Cantor analyst Josh Schimmer, adding that timelines for the next clinical or regulatory updates remain unclear.

The experimental immunotherapy works by directing the body’s immune cells to attack cancer more precisely while reducing side effects.

Swiss drugmaker Novartis’ Pluvicto is already approved for mCRPC, while Amgen and GSK are developing similar candidates.

As of October 15, the company said it has treated 109 patients across two early-stage studies, including heavily pre-treated ones.

It added 73% of the overall treatment population receiving the target doses of 2 mg or higher achieved at least a 50% reduction in prostate-specific antigen, a protein associated with the cancer.

A previous update from the study reported last year showed that all 16 patients enrolled at that time, who received once-weekly doses between 2 mg and 9 mg, achieved at least a 50% decline in PSA levels.

(Reporting by Sahil Pandey and Mariam Sunny in Bengaluru; Editing by Vijay Kishore)