Phase 1b expansion study initiated in taxane-naïve mCRPC patients

Janux Therapeutics, Inc. , a clinical-stage biopharmaceutical company developing a broad pipeline of novel immunotherapies by applying its proprietary technology to its Tumor Activated T Cell Engager (TRACTr) and Tumor Activated Immunomodulator (TRACIr) platforms, announced the initiation of Phase 1b expansion studies in the ongoing ENGAGER-PSMA-01 trial.

ENGAGER-PSMA-01 is a first-in-human, open-label, multicenter Phase 1 clinical trial designed to evaluate the safety, tolerability, pharmacokinetics, pharmacodynamics, and preliminary efficacy of JANX007 administered as monotherapy or in combination in adult patients with advanced metastatic castration-resistant prostate cancer.

Health Technology Insights: The Hartford’s New Research Finds Continued Need Among Gen Z Workers For Mental Health Care

In December 2024, Janux reported positive interim clinical data from the Phase 1a dose escalation portion of the trial in 16 mCRPC patients with a median of four prior lines of therapy. At that time, the median radiographic progression-free survival (rPFS) reported was 7.4 months for all 16 patients.* As of April 21, 2025, updated results** have been achieved in the same 16 patients supporting the initiation of the Phase 1b expansion studies:

  • Median rPFS of 7.5 months (n=16)
  • Median rPFS of 7.9 months for patients treated at 6mg and 9mg target doses (n=9)
  • 6-month rPFS of 65% (n=16)
  • 6-month rPFS of 78% for patients treated at 6mg and 9mg target doses (n=9)
  • Safety data remained consistent with the December 2024 data disclosure (n=16)

*8/16 patients were noted as in-progress in the December 2024 reported results.
**rPFS results based upon Kaplan-Meier estimate.

In addition, Janux has selected a CRS-mitigation strategy to support the initiation of the Phase 1b expansion studies that is designed to maintain the CRS profile reported in December.

The first Phase 1b expansion study will enroll taxane-naïve mCRPC patients and is designed to generate additional safety and efficacy data in this first and second line (1L/2L) patient population. This study will assess JANX007 monotherapy at two dose regimens (0.3/2/6mg and 0.3/2/9mg) with dosing administered once weekly or once every two weeks in mCRPC patients who have progressed on or after novel hormonal therapy (NHT).

Health Technology Insights: Lyra Health Launches Centers of Excellence for Employee Support

“Initiation of the taxane-naïve study marks an important step as we begin to evaluate JANX007 in earlier-line mCRPC patient populations,” said Zachariah McIver, D.O., Ph.D., Chief Medical Officer of Janux. “While therapeutic options for mCRPC have expanded, there remains a significant need for novel, non-chemotherapeutic approaches.”

Janux plans to initiate three additional Phase 1b expansion studies, evaluating:

  • JANX007 in combination with an androgen receptor inhibitor in taxane-experienced mCRPC patients
  • JANX007 monotherapy in PARP inhibitor-resistant mCRPC patients
  • JANX007 monotherapy in NHT- and taxane-experienced mCRPC patients designed to support OPTIMUS dose selection for registrational studies

“Improved efficacy and durability of responses has been observed by other prostate cancer drugs and TCEs when moving into earlier lines of therapy. There are also indications that safety with TCEs improve in earlier lines of therapy where disease burden is lower. We believe that these observations, coupled with the data seen in our Phase 1a dose escalation in later line patients, strongly support our decision to develop JANX007 in earlier lines of therapy,” said David Campbell, Ph.D., President and CEO of Janux.

Additional data from JANX007 and JANX008 will be presented at future Janux events in the second half of 2025. Separately, Janux will host an R&D Day in mid-2025 highlighting product candidates identified from its preclinical pipeline to move into clinical trials.

Janux’s TRACTr and TRACIr Pipeline

Janux’s first clinical candidate, JANX007, is a TRACTr that targets prostate-specific membrane antigen (PSMA) and is being investigated in a Phase 1 clinical trial in adult patients with metastatic castration-resistant prostate cancer. Janux’s second clinical candidate, JANX008, is a TRACTr that targets epidermal growth factor receptor (EGFR) and is being studied in a Phase 1 clinical trial for the treatment of multiple solid cancers including colorectal carcinoma, squamous cell carcinoma of the head and neck, non-small cell lung cancer, renal cell carcinoma, small cell lung cancer, pancreatic ductal adenocarcinoma and triple-negative breast cancer. We are also generating a number of additional TRACTr and TRACIr programs for potential future development, some of which are at development candidate stage or later. We are currently assessing priorities in our preclinical pipeline.

Health Technology Insights: AdvancedMD Survey: 44% of Practices to Renegotiate Rates

To participate in our interviews, please write to our HealthTech Media Room at sudipto@intentamplify.com

Source – businesswire