Janux Therapeutics Announces First Participant Dosed in Phase 1 Study of JANX014

-JANX014 expands Janux's PSMA tumor-activated T cell engager portfolio

-JANX007 is the Company's lead prostate cancer program and primary development priority

-JANX013, a PSMA-TRACIr CD28 co-stimulatory program, planned to enter the clinic in 2H2026

Janux Therapeutics, Inc. (NASDAQ:JANX) (Janux), a clinical-stage biopharmaceutical company developing a broad pipeline of novel immunotherapies, today announced that the first patient has been dosed in a Phase 1 clinical trial of JANX014 in patients with metastatic castration-resistant prostate cancer (mCRPC). JANX014 is a double-masked, prostate-specific membrane antigen (PSMA) directed T cell engager (TCE) designed to leverage Janux's tumor-activated technology platform to selectively activate T cells in the tumor microenvironment.

Janux is building a portfolio of tumor-activated PSMA therapies designed to address multiple treatment settings and mechanisms of immune engagement. Early clinical data from JANX007 have demonstrated what Janux believes is potentially a best-in-class clinical profile in mCRPC, including a favorable safety profile with no Grade 3 cytokine release syndrome observed at clinically relevant dose levels using the current CRS mitigation strategy. These data continue to guide Janux's development strategy in prostate cancer. JANX014 represents an exploratory extension of the strategy, emerging from platform work initiated in early 2024 evaluating multiple PSMA-directed approaches. JANX014 will also explore potential future use cases where enhanced safety margins and ease of administration may be particularly important.

"We are pleased to have initiated clinical evaluation of JANX014," said David Campbell, Ph.D., President and Chief Executive Officer of Janux Therapeutics. "JANX007 remains our lead prostate program, and we believe it has established a strong clinical foundation for PSMA-directed TRACTr therapy. Insights from programs such as JANX007 and JANX008 have informed our continued platform development. We are building a prostate cancer portfolio designed to address patients across multiple stages of disease, including both single and combination approaches. Advancing programs such as JANX014 reflects our strategy of expanding on that foundation while maintaining disciplined execution on our lead program."

William Go, M.D., Ph.D., Chief Medical Officer of Janux Therapeutics, added, "Janux's tumor-activated technology allows us to evaluate multiple molecular designs against the same validated target. As we advance JANX007, we are also developing complementary approaches within our platforms, including JANX013, our CD28 co-stimulatory PSMA-TRACIr program, along with exploratory approaches like JANX014. This innovative work is intended to help us understand how different mechanisms and masking strategies may translate into clinical benefit across patient populations in prostate cancer."

The Phase 1 study is a first-in-human, open-label, multicenter study to assess the safety, tolerability, pharmacokinetics, pharmacodynamics, and preliminary efficacy of JANX014 in adults with mCRPC.

Additional information about the study will be available at clinicaltrials.gov.

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's lead clinical candidate, JANX007, is a PSMA-targeted TRACTr being investigated in a Phase 1 clinical trial in patients with metastatic castration-resistant prostate cancer (mCRPC). The Company is also advancing additional PSMA-targeted programs, including JANX014, a double-masked PSMA TRACTr being evaluated in a Phase 1 clinical trial, and JANX013, a CD28 co-stimulatory TRACIr designed for combination with JANX007.

Beyond its prostate cancer programs, Janux's pipeline includes JANX008, an EGFR-targeted TRACTr being studied in a Phase 1 clinical trial in multiple solid tumors, and JANX011, a CD19-targeted ARM being evaluated in a Phase 1 clinical trial in healthy adult volunteers for potential treatment of autoimmune diseases. Janux continues to generate additional TRACTr, TRACIr, and ARM programs for potential future development.

For more information, please visit www.januxrx.com and follow us on LinkedIn.

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 and planned preclinical studies and clinical trials, the potential benefits of Janux's product candidates and platform technologies, and expectations regarding the use of Janux's platform technologies to generate novel product candidates. 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 at www.sec.gov. Such forward-looking statements are current only as of the date they are made, and Janux assumes no obligation to update any forward-looking statements, whether as a result of new information, future events or otherwise. All forward-looking statements are qualified in their entirety by this cautionary statement, which is made under the safe harbor provisions of the Private Securities Litigation Reform Act of 1995.

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