Janux Therapeutics announced positive updated interim clinical data for its JANX007 clinical program, a PSMA-TRACTr, currently in Phase 1a clinical trial for patients with advanced or metastatic castration-resistant prostate cancer (mCRPC). The data supports the selection of doses for Phase 1b expansion trials targeting pre-PLUVICTO® 2L and 3L patients.
The Phase 1a trial enrolled heavily pre-treated mCRPC patients, with a median of four prior lines of therapy. As of the November 15, 2024, data cutoff, 16 pre-PLUVICTO® patients were treated once-weekly at target doses ranging from 2 mg to 9 mg. The results showed high PSA response rates and deep PSA declines across all doses.
Efficacy Outcomes
Data from the Phase 1a trial indicated:
- 100% of patients achieved best PSA50 declines.
- 63% of patients achieved best PSA90 declines.
- 31% of patients achieved best PSA99 declines.
- 75% of patients maintained PSA50 declines at ≥ 12 weeks at a target dose ≥ 2 mg.
- 50% of patients maintained PSA90 declines at ≥ 12 weeks at a target dose ≥ 2 mg.
- In RECIST-evaluable patients, 50% (4/8) showed confirmed and unconfirmed partial responses.
According to David Campbell, Ph.D., President and CEO of Janux Therapeutics, these data provide compelling support for the selected doses in expansion trials. He stated, "These clinical data show substantial activity with JANX007 in 5L metastatic castration-resistant prostate cancer patients and provide compelling support for the doses we’ve selected for expansion trials directed at pre-PLUVICTO® 2L and 3L patients."
Safety Profile
JANX007 demonstrated a well-tolerated safety profile. Cytokine release syndrome (CRS) and treatment-related adverse events (TRAEs) were primarily limited to cycle 1 and grades 1 and 2. The maximum tolerable dose has not yet been reached.
Next Steps
Based on the efficacy and safety results, Janux has identified two once-weekly step dose regimens for Phase 1b expansion trials in pre-PLUVICTO® 2L and 3L patients. The company anticipates providing another update on JANX007 in 2025.
About JANX007
JANX007 is Janux’s first clinical candidate, a Tumor Activated T Cell Engager (TRACTr) that targets prostate-specific membrane antigen (PSMA). It is currently being investigated in a Phase 1 clinical trial in adult patients with mCRPC.
