Janux Therapeutics Reports Encouraging Interim Phase 1 Data for JANX007 in mCRPC, Highlighting Strong Efficacy and Manageable Safety Profile
Janux Therapeutics, Inc. a clinical-stage biopharmaceutical company pioneering novel immunotherapies through its proprietary platforms—Tumor Activated T Cell Engager (TRACTr), Tumor Activated Immunomodulator (TRACIr), and Adaptive Immune Response Modulator (ARM)—today announced updated interim data from its Phase 1 clinical program of JANX007, a PSMA-directed TRACTr, in patients with metastatic castration-resistant prostate cancer (mCRPC). The company will host a virtual event on Monday, December 1, 2025, at 4:30 PM ET to present the findings and provide additional insights into the ongoing development of JANX007.
Promising Efficacy with a Favorable Safety Profile
Janux’s updated interim data demonstrate that JANX007 continues to show robust anti-tumor activity alongside a manageable safety profile, including cytokine release syndrome (CRS) predominantly limited to early treatment cycles and mostly grades 1 and 2. These data were derived from both the Phase 1a dose escalation cohort and the Phase 1b expansion cohort, representing a broad spectrum of patients, including heavily pre-treated and taxane-naïve individuals.
“We are pleased that JANX007 achieved durable responses with a manageable safety profile that compares favorably to both approved and investigational therapies in mCRPC,” said David Campbell, Ph.D., President and CEO of Janux Therapeutics. “Additionally, we found that the ability to transition patients to every two-week dosing (Q2W) may provide meaningful convenience advantages for patients. We are eager to further evaluate JANX007 in earlier-line mCRPC, where improved tolerability and durability could have an even greater clinical impact.”
Dr. Eleni Efstathiou, Section Chief of Genitourinary Medical Oncology at Houston Methodist Cancer Center and investigator on the trial, added, “The early data with JANX007 are highly encouraging. I am deeply committed to this program and inspired by its potential to transform care for patients with mCRPC, particularly as its role in earlier-line treatment is explored.”
Phase 1 Clinical Program Design and Patient Population
As of the October 15, 2025, data cutoff, a total of 109 patients have been treated with JANX007 across both the Phase 1a dose escalation and Phase 1b expansion studies. Patients enrolled in the Phase 1a trial were heavily pre-treated, with a median of four prior lines of therapy, while Phase 1b focused on taxane-naïve mCRPC patients.
Across both cohorts, JANX007 demonstrated high prostate-specific antigen (PSA) response rates and significant PSA declines, suggesting potent anti-tumor activity. Among RECIST-evaluable patients, 30% (8 of 27) experienced partial responses, including both confirmed and unconfirmed responses, underscoring the therapy’s clinical potential.
Encouraging Durability and Early Indicators of Progression-Free Survival
One of the key findings from the ongoing trials is the durability of JANX007’s anti-tumor responses. Patients in both the once-weekly (QW) and Q2W dosing groups exhibited radiographic progression-free survival (rPFS) ranging from 7.9 to 8.9 months. Notably, the rPFS observed in the Q2W expansion cohort compared favorably with that of the QW cohort, suggesting that less frequent dosing could maintain efficacy while potentially enhancing patient convenience and adherence.
Preliminary Phase 1b data from taxane-naïve patients were particularly promising, with rapid and deep PSA reductions observed and CRS events primarily limited to grade 1 severity. Tumor burden analyses also suggest the potential for improved rPFS in patients treated earlier in the mCRPC disease course, highlighting JANX007’s promise in front-line or earlier-line treatment settings.
Safety and Cytokine Release Syndrome Management
Safety remains a critical focus in the development of immunotherapies, and JANX007 continues to demonstrate a predictable and manageable safety profile. CRS, the primary safety concern associated with T-cell-engaging therapies, was largely confined to cycle 1 and predominantly grades 1 and 2. Importantly, the Janux team has developed a CRS mitigation strategy that maintains this favorable safety profile without compromising anti-tumor activity.
“These findings with JANX007 demonstrate strong efficacy and a CRS safety profile that is predictable and manageable,” said Dr. Benjamin Garmezy, Associate Director of Genitourinary Cancer Research and Executive Co-Chair of the Genitourinary Cancer Research Executive Committee at Sarah Cannon Research Institute (SCRI). “This enables clinicians to confidently anticipate and address CRS promptly and effectively during early treatment cycles, which is crucial for patient safety and overall treatment success.”
Strategic Development Plans
Janux is advancing JANX007 with a focus on monotherapy as well as combination therapy with darolutamide in taxane-naïve mCRPC patients. This segment of the patient population is expanding due to the increasing use of androgen receptor pathway inhibitors (ARPIs) in hormone-sensitive prostate cancer (HSPC), making it a key target for therapeutic innovation.
In addition, Janux plans to explore JANX007 in patients who are refractory to PARP inhibitors, a population with significant unmet need. Positive outcomes in this setting may provide a potential pathway toward expedited regulatory approval.
Webcast and Investor Information
Janux will host a live webcast of the Phase 1 data presentation today at 4:30 PM ET, followed by a live analyst Q&A session. Investors and interested parties are encouraged to register through the company’s website. The webcast replay will remain available in the Investors section of Janux’s website (https://investors.januxrx.com) for at least 30 days following the event.
Broad TRACTr, TRACIr, and ARM Pipeline
JANX007 represents the first clinical candidate from Janux’s innovative TRACTr platform, targeting prostate-specific membrane antigen (PSMA) for the treatment of mCRPC. The company’s second clinical candidate, JANX008, is a TRACTr targeting epidermal growth factor receptor (EGFR), currently in a Phase 1 trial for multiple solid tumors, 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.
In addition to these programs, Janux is advancing multiple CD3-based TRACTr and CD28-based TRACIr programs for future clinical development, including:
- A PSMA-directed TRACIr designed for combination therapy with JANX007.
- A TROP2-targeted TRACTr for the treatment of TROP2-positive solid tumors.
Janux is also developing its first ARM platform candidate, a CD19-ARM, aimed at the potential treatment of autoimmune diseases. Furthermore, the company continues to generate additional TRACTr, TRACIr, and ARM programs to expand its pipeline and address a broad range of oncology and immunology indications.
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