Spero suspends development of SPR720, to reduce workforce by 39%

Spero Therapeutics (SPRO) announced that a planned interim analysis of the Phase 2a proof-of-concept study of SPR720 for the treatment of NTM-PD demonstrated that the program did not meet its primary endpoint. While the data showed antimicrobial activity associated with SPR720, the interim analysis did not show sufficient separation from placebo and highlighted potential dose limiting safety issues in subjects dosed at 1,000 mg orally once daily, including three cases of reversible grade 3 hepatotoxicity. In evaluating the totality of both the efficacy and safety data, the company has elected to suspend its current development program for SPR720 and will evaluate other potential paths forward as the remaining data are collected and analyzed. As a result of the suspension of the current SPR720 development program, Spero will undergo a restructuring and reduction in force of approximately 39%, which will extend cash runway and support operations into mid-2026, to further support the development of tebipenem HBr, SPR206, and potential strategic activities. Following the reduction in force and restructuring, Spero estimates that its existing cash and cash equivalents, together with earned and non-contingent development milestone payments from GSK, as well as other non-dilutive funding commitments, will be sufficient to fund its operating expenses and capital expenditures into mid-2026. During this period, the company remains focused on advancing tebipenem HBr in the ongoing global PIVOT-PO Phase 3 clinical trial and preparing for a Phase 2 clinical trial for SPR206 contingent on continued non-dilutive funding.