Spero Therapeutics licenses anti-CD40L antibody SP001 from Innovent
Spero Therapeutics has signed an exclusive licence with Innovent Biologics for SP001 (IBI355), a third-generation Fc-silent anti-CD40L monoclonal antibody, in a transaction with a total potential value of approximately US$1.1 billion. Spero receives rights to develop, manufacture and commercialise the asset worldwide except Greater China, where Innovent retains control.
Innovent will receive an undisclosed upfront payment, plus development, regulatory and commercial milestone payments that could reach $1.1 billion in aggregate, and tiered royalties on net sales in Spero's licensed territories. The upfront figure was not disclosed in the release.
The science and the lead indication
SP001 targets CD40L, an upstream immune activation signal involved in the interaction between T cells, B cells and antigen-presenting cells. The antibody is described as "Fc-silent", a design modification intended to eliminate platelet activation risks that were associated with earlier-generation anti-CD40L antibodies and contributed to setbacks in the class. The third-generation label reflects both this safety engineering and a fully humanised IgG1 scaffold that retains FcRn interaction, supporting a conventional antibody half-life.
Innovent has completed two Phase 1 healthy-volunteer studies (single and multiple ascending dose) and a Phase 1b multiple ascending dose study in patients with Sjögren's disease (SjD). Data from the SjD Phase 1b were presented as a poster at the EULAR 2026 Congress, though the release did not summarise efficacy or safety findings in quantitative terms.
Spero plans to start a Phase 2 trial in IgG4-related disease (IgG4-RD) in the second quarter of 2027. IgG4-RD is a chronic fibroinflammatory condition affecting multiple organs, including the pancreas, kidneys and salivary glands. Current management leans heavily on steroids and B-cell-depleting agents; there are no approvals specifically targeting the underlying CD40L-driven pathology. Innovent, meanwhile, expects to initiate its own Phase 2 in SjD in China by early 2027.
Esther Rajavelu, President and Chief Executive Officer of Spero Therapeutics, framed the deal as the foundation of a new pipeline direction following the company's prior focus on infectious diseases. Dr Arezou Khosroshahi, Professor of Medicine at Emory University School of Medicine, noted that a non-B-cell-depleting approach to CD40L inhibition "could represent an important area for clinical evaluation in IgG4-RD".
Market context and competitive positioning
The CD40L pathway has attracted renewed interest after years of dormancy following platelet safety concerns with first-generation agents. Several biotechs are now pursuing redesigned molecules, and the pathway's breadth across autoimmune indications makes it attractive for platform-style development. IgG4-RD itself is a relatively rare condition with a growing diagnostic base, aided by increased clinician awareness; the US patient population is estimated in the tens of thousands, which places it in a niche where orphan incentives may apply alongside meaningful unmet need.
Spero's repositioning from antimicrobials into immunology is a notable strategic pivot. The company's previous commercial-stage asset was in uncomplicated urinary tract infections, a very different competitive and reimbursement environment. Investors will want to see a clear path to proof-of-concept Phase 2 data before the $1.1 billion milestone stack carries much weight in valuation models.
Broader autoimmune licensing activity has been brisk in 2025 and 2026, with several large-cap pharma companies acquiring or optioning assets targeting T-cell and B-cell co-stimulatory pathways. Spero's ex-China structure mirrors a common deal architecture in which a Chinese innovator retains its home market while a Western partner drives registration strategy in the US and Europe.
The next clinical milestone to watch is the Phase 2 start in IgG4-RD, expected in Q2 2027, and the readout from Innovent's concurrent SjD study, which may generate the first controlled efficacy signal for the molecule.