Theriva Biologics sells SYN-004 (ribaxamase) portfolio to Biossil Labs

Theriva Biologics, Inc. (NYSE American: TOVX) entered into an Asset Purchase and Sale Agreement with Biossil Labs Inc. on October 30, 2026, with the transaction closing the same day. Under the agreement, Theriva sold Biossil its assets exclusively relating to SYN-004 (ribaxamase), its oral β-lactamase product candidate, including improvements and reformulations such as SYN-007, as well as certain assets tied to the carbapenemase candidate SYN-006.¹

Biossil paid Theriva a non-refundable, non-creditable upfront payment of $350,000 at closing.¹ Beyond that upfront sum, Theriva is eligible for two separate payment streams. First, milestones: up to $3 million in regulatory milestones tied to first FDA approval and first EMA marketing authorization, and up to $88 million in sales milestones tied to cumulative worldwide net sales thresholds¹, for a combined milestone total of $91 million. Second, royalties: a running low-single-digit royalty on worldwide net sales of ribaxamase, SYN-006, and related products, capped separately at $250 million, plus a low-double-digit share of certain license consideration Biossil receives, which is not subject to the royalty cap.¹

Biossil has sole control over development and commercialization and has agreed to use commercially reasonable efforts to advance at least one product to regulatory approval.¹ Separately, Theriva amended a 2012 agreement with PREV ABR LLC, under which it paid PREV $140,000 at closing and will owe PREV a share of future milestone, royalty, and license payments tied to the sold assets, subject to an aggregate cap of $13.0 million¹.

Theriva CEO Steven A. Shallcross said the sale allows continued clinical development of the portfolio, including advancement of the Phase 1b/2a clinical trial at Washington University investigating prevention of acute graft-versus-host disease and opportunistic infections in antibiotic-treated allogeneic hematopoietic cell transplant recipients.¹