Spero Therapeutics (SPRO) Registration filing summary

Company overview and business model

• Clinical-stage biopharmaceutical company focused on next-generation medicines for immune-mediated diseases.

• Lead program, SP001, is a fully humanized monoclonal antibody targeting CD40 Ligand, licensed from Innovent Biologics and Fortvita Biologics for global development (excluding certain Asian territories).

• Developing SP001 for Immunoglobulin G4 related disease, with potential for broader immune-mediated indications.

Financial performance and metrics

• As of June 30, 2026, 58,146,910 shares of common stock outstanding; pro forma up to 140,791,538 shares if full offering is completed at $1.21/share.

• Historical net tangible book value as of June 30, 2026: $44.2 million ($0.76/share); pro forma net tangible book value after offering: $141.1 million ($1.00/share).

• Immediate dilution to new investors estimated at $0.21/share if offering is completed at $1.21/share.

Use of proceeds and capital allocation

• Net proceeds intended for general corporate purposes, including clinical trials, R&D, working capital, capital expenditures, investments, acquisitions, and collaborations.

• Management retains broad discretion over allocation of proceeds.