Janux Therapeutics Announces Positive Initial Phase 1 Data for JANX011 in Healthy Volunteers, Supporting Planned Development in Patients with Autoimmune Disease

Janux Therapeutics, Inc. (JANX) (Janux), a clinical-stage biopharmaceutical company developing a broad pipeline of novel immunotherapies, today announced initial clinical results from the Phase 1 study of JANX011 in healthy volunteers and outlined its planned clinical development strategy in autoimmune diseases. JANX011 is the first program from Janux’s proprietary Adaptive Immune Response Modulator (ARM) platform to enter clinical development. The ARM platform is designed to selectively recruit a defined T-cell subset to drive deep and sustained target-cell depletion while limiting broad T-cell activation.

Following one subcutaneous dose without step-up dosing, JANX011 demonstrated deep B-cell depletion, Grade 1-only cytokine release syndrome (CRS), and selective activation of the intended TRBV6-expressing T-cell subset. Together, these findings provide initial human clinical validation of ARM and establish a strong foundation for advancing JANX011 in autoimmune disease.

“This marks an important step forward for Janux,” said David Campbell, Ph.D., President and Chief Executive Officer of Janux. “The results give us a strong foundation to advance JANX011 in autoimmune disease and provide the first human validation of ARM. We see an opportunity to build significant value both through JANX011 and by extending ARM across additional targets and indications.”

Initial Phase 1 Clinical Results

The Phase 1 study evaluated the safety, tolerability, pharmacokinetics and pharmacodynamics of JANX011 in healthy volunteers. The initial dataset includes 25 participants across five single-ascending-dose cohorts ranging from 30 µg to 3 mg. JANX011 was administered subcutaneously and without step-up dosing. The study was designed to characterize human pharmacology and establish an initial activity and tolerability profile to inform subsequent development in autoimmune patient studies. The data presented reflect a November 2, 2026 data cutoff.

Key findings from the initial clinical data include:

• Deep, dose-dependent B-cell depletion: JANX011 produced deep B-cell depletion at both 1 mg and 3 mg. At 3 mg, 3/5 participants achieved greater than 90% depletion, including two with B-cell counts below the limit of detection.
  
  
• Sustained B-cell depletion: Reductions in peripheral B-cell counts persisted through Day 42 following a single dose of JANX011.
  
  
• Grade 1-only CRS: No CRS was reported among 16 participants treated at 30 to 300 µg. Grade 1 CRS occurred in one of four participants at 1 mg and four of five participants at 3 mg. All events resolved with acetaminophen, and no CRS event exceeded Grade 1.
  
  
• Overall safety and tolerability: JANX011 was well-tolerated. No serious adverse events or dose-limiting toxicities were reported across 25 participants, and other treatment-related adverse events were predominantly Grade 1. At 3 mg, one Grade 3 ALT elevation and Grade 2 ALT and AST elevations were observed. The elevations were transient, asymptomatic and did not require treatment.
  
  
• Limited inflammatory cytokine induction: Limited increases in IL-6, TNFα, IFNγ and IL-2 were observed, consistent with the Grade 1-only CRS profile.
  
  
• Selective TRBV6 T-cell activation: JANX011 produced dose-responsive activation of TRBV6-expressing CD4 and CD8 T cells, with limited activation of TRBV6-negative T cells. TRBV6-expressing T cells represented approximately 10% of circulating T cells across the healthy volunteers evaluated.
  
  

Together, these observations support ARM’s design of selectively recruiting a defined T-cell subset to drive deep target-cell depletion while limiting broad T-cell activation. This initial human profile provides a strong foundation for advancing JANX011 in autoimmune disease.

JANX011 Clinical Development Strategy

Based on the initial clinical findings, Janux plans to advance JANX011 into autoimmune patient studies, initially in immune thrombocytopenia (ITP) and rheumatoid arthritis (RA), with study initiations targeted for the first and second halves of 2027, respectively.

ITP and RA were selected as initial indications to establish clinical proof of concept and characterize JANX011’s potentially differentiated clinical profile. ITP provides an early, objective measure of clinical activity through platelet response, while RA provides an opportunity to develop JANX011 in a larger, established autoimmune indication to further characterize dose, regimen, durability and clinical activity. Across both indications, Janux aims to evaluate the potential of JANX011 to deliver meaningful clinical benefit to patients through targeted B-cell depletion with a favorable safety profile and convenient dosing regimen.

The healthy-volunteer study established a strong starting point for patient development and further optimization of dose and regimen.

About JANX011

JANX011 is an investigational CD19-targeted bispecific T-cell engager and the first clinical-stage candidate from Janux’s proprietary Adaptive Immune Response Modulator (ARM) platform. It is designed to selectively engage T cells through the conserved TRBV6 domain rather than CD3 and is being developed for the potential treatment of autoimmune diseases.

Initial Human Validation of the ARM Platform

The ARM platform is designed to selectively recruit a defined T-cell subset rather than broadly engage T cells through CD3. Initial human results with JANX011 link selective TRBV6 T-cell activation with deep B-cell depletion and Grade 1-only CRS, supporting the ARM design. Janux believes these findings provide a foundation for extending ARM across additional targets and formats.

Investor Webcast Information

Janux will host an investor webcast today, November 9, 2026, at 8:30 a.m. ET to review the initial JANX011 clinical results and discuss its planned autoimmune development strategy. The webcast will include a management presentation followed by a live question-and-answer session.

The presentation and webcast will be accessible through the Events and Presentations section of the Janux website.

Analysts and investors wishing to participate in the live Q&A may use the participant callback link to enter their contact information and receive an automated call connecting them to the event. Alternatively, participants may dial 877-346-6112 (U.S. and Canada toll-free) or +1-848-280-6350 (international).

A replay of the webcast will be available for at least 30 days following the event.

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 and being evaluated in a Phase 1 clinical trial.

Beyond its prostate cancer programs, Janux’s pipeline includes JANX011, a CD19-targeted ARM being evaluated in a Phase 1 clinical trial in healthy adult volunteers for the 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 Janux on LinkedIn.

Forward-Looking Statements

This news release contains certain forward-looking statements that involve risks and uncertainties that could cause actual results to differ materially 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, the timing, scope and results of Janux’s development activities; plans to advance JANX011 into autoimmune patient studies; plans to evaluate step-up and repeat dosing; the targeted timing for initiation of studies in ITP and RA; the potential characteristics, safety, tolerability, efficacy, convenience and therapeutic effects of JANX011; the potential application of the ARM platform across additional targets, formats, indications and disease settings; 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 or early clinical results may not be predictive of later or final results; clinical outcomes may change as additional data are generated, follow-up continues and analyses are reviewed; product candidates that appear promising in early research or clinical development may not demonstrate safety or efficacy in later studies; Janux may experience delays in clinical development, regulatory review, manufacturing or enrollment; Janux may not obtain regulatory approval for its product candidates; and other risks described in Janux’s filings with the Securities and Exchange Commission, which are available at www.sec.gov. Forward-looking statements are current only as of the date they are made, and Janux assumes no obligation to update them, except as required by law. All forward-looking statements are qualified in their entirety by this cautionary statement and the safe harbor provisions of the Private Securities Litigation Reform Act of 1995.

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