Tonix Pharmaceuticals Publishes Phase 1 Data for Fc-Modified Anti-CD40L mAb TNX-1500 in Transplant Rejection

Phase 1 data published in the Journal of Clinical Immunology position Tonix Pharmaceuticals' TNX-1500 as a potential first-in-class entry in a target class where no anti-CD40L monoclonal antibody has yet reached approval, a gap that carries direct implications for CMC teams and regulatory leads preparing for the next development stage.

TNX-1500 is a third-generation, Fc-modified IgG4 anti-CD154 mAb engineered to address the thromboembolic safety liabilities observed with first-generation anti-CD40L constructs, while retaining Fc-mediated effector functions and a clinically useful half-life. The first-in-human, randomized, double-blind, placebo-controlled, single-ascending dose study enrolled 26 healthy adult volunteers across three dose cohorts, 3, 10, and 30 mg/kg, with a 120-day follow-up period. TNX-1500 blocked the primary T cell-dependent antibody response to keyhole limpet hemocyanin at all dose levels and suppressed the secondary response at 10 and 30 mg/kg; at 3 mg/kg, peak secondary response was reduced by approximately 70% relative to placebo.

From a tolerability standpoint, no serious adverse events were recorded and no participants discontinued due to adverse events. The sole treatment-emergent adverse event considered possibly related to study drug was aphthous ulcer, reported in one participant per active cohort; all events were rated mild and resolved within 2 to 10 days. Notably, no administration-site or injection-site reactions were observed, a prespecified adverse event of special interest given the intravenous delivery route. Pharmacokinetic analyses indicated approximately dose-proportional exposure across the full dose range, with mean terminal elimination half-lives of 37.8 and 33.8 days at the 10 and 30 mg/kg levels, supporting a monthly intravenous dosing interval.

For manufacturing and regulatory teams, the Fc-modification strategy in TNX-1500 introduces specific CMC considerations that will require careful documentation ahead of any Phase 2 IND submission. Fc-engineered constructs present distinct characterisation requirements under ICH Q6B and demand robust comparability protocols if process changes occur between clinical phases. The investigator-initiated Phase 2 study planned at Massachusetts General Hospital is contingent on FDA clearance of MGH's IND application, with initiation targeted for the second half of 2026; that timeline sets a near-term checkpoint for both the sponsor's CMC package and the site's regulatory readiness.

The Phase 2 IND clearance decision will serve as the first measurable regulatory signal for this Fc-modified construct in an allograft rejection indication.

Source: Tonix Pharmaceuticals Holding Corp. via GlobeNewswire press release, 27 May 2026.