Janux's shares jump 130% as analysts see blockbuster potential in phase 1 T-cell engager data

Janux Therapeutics’ executives aren’t the only ones celebrating positive interim phase 1 data from two tumor-focused candidates, with analysts touting their blockbuster potential and investors doubling the biotech’s share price this morning.

The candidates in question are a tumor-activated T-cell engager called JANX007, which is being tested in patients with advanced or metastatic prostate cancer, and JANX008, which is being trialed in advanced or metastatic solid tumors expressing high levels of EGFR.

A total of 23 patients had been treated with JANX007 as of Feb. 12, as part of the dose-escalation portion of a phase 1a trial. Of the 18 patients who received a starting dose of 0.1 mg, 14 (78%) achieved a prostate specific antigen (PSA) decline of at least 30%, with 10 of those patients (56%) achieving a decline of 50%.

All six of the patients who received a 0.2-mg starting dose of JANX007 achieved a 30% reduction of PSA, with five of the six achieving a 50% reduction, Janux reported in the Feb. 26 postmarket release.

“Initial step doses of JANX007 ≥ 0.2 mg drove deeper and more durable PSA responses, including one subject that achieved a [90%] decline,” the biotech added.

Cytokine release syndrome (CRS)—a severe immune reaction that has haunted other biotechs’ T-cell therapy trials—was observed in the study, but Janux stressed that the cases were “temporary … presenting only as low-grade 1 or 2 events, and was quickly managed with treatment.”

“These incidents of CRS were mainly reported during the first treatment cycle, with no subsequent occurrences in later cycles,” the company added. Most non-CRS adverse events related to treatment were of low severity and also mainly occurred in the initial treatment cycle, with no grade 4 or 5 events reported.

By the same review point, 11 patients with either colorectal cancer, squamous cell carcinoma of the head and neck, non-small cell lung cancer (NSCLC) or renal cell carcinoma (RCC) were treated in the JANX008 phase 1a trial at doses of up to 1.25 mg. Janux said the drug has shown “encouraging signs of clinical activity,” including a NSCLC patient who saw a 100% reduction in their target lung lesion and no cancer growth beyond the liver, along with no CRS or treatment-related adverse events.

The other patient Janux picked out had a 12% reduction in their RCC, although they also experienced grade 1 CRS. Only one other patient experienced CRS and this was also grade 1, according to the biotech.

Based on the safety profiles of both drugs, Janux is continuing dose optimization for both trials. The company expects to provide an update on JANX007 doses for expansion in the second half of 2024.

The readouts “provide compelling proof-of-concept” for Janux’s TRACTr platform, which has been designed to “provide an entry point to multiple, large solid tumor indications that are intractable with conventional T-cell engager approaches,” CEO David Campbell, Ph.D., said in the release.

Analysts at William Blair also saw the potential in the tech, saying that yesterday’s readout had raised their estimation of JANX007’s success from 40% up to 60%.

“We estimate peak sales of $1.5 billion in chemotherapy refractory metastatic prostate cancer, but moving the treatment into earlier lines of the treatment paradigm creates multi-blockbuster potential,” they said in a Feb. 27 note.

Investors appeared similarly enthused, with Janux’s stock beginning trading on Tuesday at $36.27—a 137% increase on the $15.10 closing price on Monday.