(Nasdaq: JANX) (Janux), a clinical-stage biopharmaceutical company developing a broad pipeline of novel immunotherapies by applying its proprietary technologies to its Tumor Activated T Cell Engager (TRACTr), Tumor Activated Immunomodulator (TRACIr), and Adaptive Immune Response Modulator (ARM) platforms, today announced positive updated interim data for its JANX007, a PSMA-directed TRACTr, Phase 1 clinical program in patients with mCRPC. Janux will host a virtual event on Monday, December 1, 2025, at 4:30 PM ET.Janux Therapeutics, Inc.

“We are pleased JANX007 achieved durable responses with a manageable safety profile that compares favorably to both approved and investigational therapies in mCRPC. Additionally, we found that the ability to transition patients to Q2W dosing may provide meaningful convenience advantages,” said David Campbell, Ph.D., President and CEO, Janux Therapeutics. “We look forward to evaluating the potential for JANX007 in earlier-line mCRPC, where improved tolerability and durability could have an even greater impact.”

“The early data with JANX007 are highly encouraging. I am deeply committed to this program and inspired by its potential to transform care for mCRPC patients, especially as its potential in earlier-line mCRPC treatment is explored,” said Dr. Eleni Efstathiou, Section Chief, Genitourinary Medical Oncology, Houston Methodist Cancer Center and investigator on the trial.

Updated Phase 1 interim clinical data for PSMA-TRACTr JANX007 in mCRPC

As of the October 15, 2025 data cutoff, a total of 109 patients have been treated across the Phase 1a dose escalation and Phase 1b expansion trials of JANX007. The patients enrolled in the Phase 1a trial were heavily pre-treated with a median of four prior lines of therapy. The patients enrolled in the Phase 1b expansion trial were taxane-naïve mCRPC.

Patients from the Phase 1 trials demonstrated high prostate-specific antigen (PSA) response rates and deep PSA declines. Anti-tumor activity was observed with confirmed and unconfirmed partial responses in 30% (8/27) of RECIST-evaluable patients.

Encouraging durability was observed in both the QW and every two week (Q2W) expansions with rPFS ranging from 7.9 to 8.9 months and the rPFS of the Q2W expansion group comparing favorably to the QW expansion group.

Preliminary Phase 1b data in taxane-naïve patients demonstrated rapid and deep PSA reductions with primarily grade 1 CRS. Additionally, tumor burden analysis suggests potential for improved rPFS in JANX007 treated earlier line patients.

JANX007 demonstrated a manageable safety profile with cytokine release syndrome (CRS) primarily limited to cycle 1 and grades 1 and 2. Additionally, a CRS mitigation strategy was identified that maintains the grade 1 and 2 CRS profile.

“These findings with JANX007 demonstrate strong efficacy and a CRS safety profile that is predictable and manageable, enabling clinicians to confidently anticipate and address CRS promptly and effectively during early treatment cycles," said Dr. Benjamin Garmezy, Associate Director, Genitourinary Cancer Research; Executive Co-Chair, Genitourinary Cancer Research Executive Committee, Sarah Cannon Research Institute (SCRI) and investigator on the trial.

Janux is advancing JANX007 with a focus on monotherapy and darolutamide combinations in taxane-naïve mCRPC patients. This is the largest and growing mCRPC setting due to increased use of ARPIs in HSPC. Janux also plans to evaluate JANX007 in PARP inhibitor refractory patients as a potential path to an expedited approval.

Webcast Information

Janux will host a live webcast today at 4:30 PM ET. A live analyst question and answer session will follow the formal presentation. To register for the event, please clickhere

To access the live webcast, please visit the Investors section of the Company's website. A replay of the webcast presentation will be available on the Company's website athttps://investors.januxrx.com

Janux’s TRACTr, TRACIr and ARM 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 mCRPC. 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. Janux is also advancing additional CD3-based TRACTr and CD28-based TRACIr programs for future clinical development, including a PSMA-TRACIr for use in combination with our PSMA-TRACTr JANX007, and a TROP2-TRACTr for the treatment of TROP2+ solid tumors. Janux is advancing its first ARM platform program candidate, a CD19-ARM for the potential treatment of autoimmune diseases toward clinical trials. Janux is also generating a number of additional TRACTr, TRACIr and ARM programs for potential future development.

About Janux Therapeutics

Janux is 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), Tumor Activated Immunomodulator (TRACIr), and Adaptive Immune Response Modulator (ARM) platforms. Janux has two TRACTr therapeutic candidates in clinical trials, the first targeting PSMA is in development for prostate cancer, and the second targeting EGFR is being developed for 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. For more information, please visitwww.januxrx.com

Forward-Looking Statements

This news release contains certain forward-looking statements that involve risks and uncertainties that could cause actual results to be materially different from historical results or from any future results expressed or implied by such forward-looking statements. Such forward-looking statements include statements regarding, among other things, Janux’s ability to bring new treatments to cancer patients in need, expectations regarding the timing, scope and results of Janux’s development activities, including its ongoing clinical trials and that interim data results support continued clinical development of JANX007, and the potential benefits of Janux’s product candidates and platform technologies. Factors that may cause actual results to differ materially include the risk that interim results of a clinical trial are not necessarily indicative of final results and one or more of the clinical outcomes may materially change as patient enrollment continues, following more comprehensive reviews of the data and as more patient data becomes available, including the risk that unconfirmed responses may not ultimately result in confirmed responses to treatment after follow-up evaluations, the risk that compounds that appear promising in early research do not demonstrate safety and/or efficacy in later preclinical studies or clinical trials, the risk that Janux may not obtain approval to market its product candidates, uncertainties associated with performing clinical trials, regulatory filings and applications, risks associated with reliance on third parties to successfully conduct clinical trials, the risks associated with reliance on outside financing to meet capital requirements, and other risks associated with the process of discovering, developing and commercializing drugs that are safe and effective for use as human therapeutics, and in the endeavor of building a business around such drugs. You are urged to consider statements that include the words “may,” “will,” “would,” “could,” “should,” “believes,” “estimates,” “projects,” “promise,” “potential,” “expects,” “plans,” “anticipates,” “intends,” “continues,” “designed,” “goal,” or the negative of those words or other comparable words to be uncertain and forward-looking. For a further list and description of the risks and uncertainties Janux faces, please refer to Janux’s periodic and other filings with the Securities and Exchange Commission, which are available atwww.sec.gov

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