Quantum-Si Surges 25% as H.C. Wainwright Reiterates Buy on Proteus Amino Acid Detection Milestone

Quantum-Si shares jumped 25% on October 9, 2026, standing out sharply against a backdrop of broad de-SPAC selloffs across U.S. markets. The rally came as H.C. Wainwright reiterated its Buy rating on the stock, citing progress in the company's next-generation Proteus platform development program.

The catalyst centers on Quantum-Si's Proteus platform, which has now achieved detection of 19 of the 20 standard amino acids, a meaningful step forward from the 17 detected as of the company's Q1 2026 earnings call. The company is targeting full 20-amino acid detection and a commercial launch of Proteus by the end of 2026, with the platform designed to deliver a significant performance improvement over its commercially available Platinum Pro instrument.

The 25% single-session gain was notable given the broader market environment, in which de-SPAC stocks broadly sold off. Quantum-Si, which went public via a SPAC merger, bucked that trend on the strength of the clinical and analyst developments. H.C. Wainwright maintained its price target alongside the reiterated Buy rating.