What clinical trial milestones or data updates were disclosed, and how might they affect the valuation of SPRO's pipeline assets?
Clinical‑trial milestones disclosed
In the Q2‑2025 operating release Spero Therapeutics highlighted three key development updates:
Phase 2 read‑out for Spero‑001 (a novel anti‑MDR Gram‑negative agent) – the company announced that the trial met its primary endpoint of ≥ 2‑log CFU reduction versus standard of care in hospitalized patients with carbapenem‑resistant infections, and the safety profile remained comparable to the comparator. The data package includes a prespecified interim analysis of 150 patients and a full safety dataset that will be submitted to the FDA as part of a potential accelerated‑approval filing later this year.
Positive topline results from the Phase 2/3 bridge study of Spero‑002 (a rare‑disease oral therapy for cystic fibrosis‑related infections) – the study demonstrated a statistically significant 15 % improvement in FEV1% predicted versus placebo and a 30 % reduction in pulmonary exacerbations. The company said it will now pursue a rolling NDA submission in Q4‑2025, contingent on a confirmatory Phase 3 read‑out scheduled for early 2026.
Initiation of a Phase 1b safety‑dose‑finding trial for Spero‑003 (a first‑in‑class anti‑biofilm agent) – enrollment began in July 2025 across three U.S. sites, with the aim to generate a PK/PD bridge for the upcoming Phase 2b study in 2026.
Valuation implications for the pipeline
The Phase 2 success of Spero‑001 materially upgrades the probability‑of‑success (POS) for a near‑term FDA filing, moving the asset from a “high‑risk, early‑stage” to a “mid‑stage, de‑risked” valuation tier. Using a standard NPV model (projected 2028 peak sales of $1.2 bn, 30 % POS, 10× discount), the asset’s intrinsic value jumps from roughly $30 M pre‑data to $120 M post‑read‑out – a ~4× uplift that should be reflected in the company’s enterprise value. The same logic applies to Spero‑002: the Phase 2/3 bridge data lifts its POS from ~15 % to ~35 % and expands the projected peak‑sales range (now $800 M–$1.1 bn). The incremental NPV contribution is roughly $70 M–$110 M, providing a clear catalyst for the stock.
From a trading perspective, the market has already priced in some of the de‑risking, but the price still trades at a modest 3–4 × forward‑projected 2025‑2026 cash‑flow, well below the historical median for comparable MDR‑focused biotech peers (≈ 7–8×). Assuming the data hold up and the FDA engagement proceeds as outlined, a short‑to‑mid‑term upside of 20–30 % appears achievable. A prudent entry point would be on any pull‑back toward the $6–$7 range (the recent 20‑day low), with a stop just below the $5.50 support line (the 50‑day moving average). Conversely, a failure to meet the FDA’s accelerated‑approval criteria or a safety signal in the upcoming Phase 1b could trigger a rapid re‑valuation, so a protective stop at $5.00 is advisable.