Spero Therapeutics said its lead follow-on asset, SP001, will enter a Phase II trial in IgG4-related disease (IgG4-RD) in the second quarter of 2027. The company outlined the plan at the 3rd Annual Guggenheim Healthcare Innovation Conference.
SP001 is a third-generation anti-CD40 ligand antibody that Spero in-licensed from Innovent Biotech in July 2024. Management said the deal came with $105 million in non-dilutive, non-recourse funding. The company said it had about $50 million in cash as of June 2024. Spero's president and CEO, Esther Rajavelu, said the package allows the asset to move into the clinic without adding near-term financing pressure.
Spero said SP001 uses a silent Fc region, which it believes addresses the thromboembolic risk linked to earlier CD40 ligand drugs. Management stressed that this risk is tied to the Fc region, not to the CD40 ligand target itself.
The Phase II trial will be open-label, with two dose cohorts and a six-month treatment period. The primary endpoint is the IgG4 responder index. Secondary endpoints include safety, tolerability and biomarker evaluation. Management said dosing will draw on prior human data from Innovent and on Spero's own clinical work. Roughly 100 human subjects have been exposed to SP001 across healthy volunteer studies and a Sjögren's program. Management said it is too early to set a flare-reduction target before Phase II data are available.
Spero cited Innovent's Phase I-B study in Sjögren's syndrome. The study enrolled about 30 patients in China and tested doses of 7.5 mg/kg, 15 mg/kg and 30 mg/kg. Rajavelu said the drug was tolerated across all doses and that placebo-adjusted improvements appeared at all three doses. Upper respiratory infections occurred across dose groups compared with placebo, but Rajavelu said there was no dose-dependent pattern. Spero said it will watch infection risk closely in future studies.
Spero said Innovent ran head-to-head preclinical comparisons against agents from Amgen and Sanofi. In an anti-KLH mouse model, the company said SP001 showed greater potency than frexalimab, Sanofi's late-stage anti-CD40L drug. Management cautioned that this potency still needs clinical validation.
Investing.com, the source of the report, also noted that SPRO shares have fallen 58% over the past six months, trading at $1.03 against a 52-week high of $3.08.