Why Summit Therapeutics Inc. (SMMT) Stock Rose 6.5% on Aug 26, 2026

The clearest new catalyst: Phase III HARMONi-GI1 trial success.

Researched by BestStocks Market Desk · Published Aug 26, 2026

Prior close

$13.36

Aug 26, 2026 close

$14.23

Change

+$0.87

+6.51%

Rel. volume

2.1×

11.6M shares

Why did SMMT stock rise?

Summit Therapeutics rose 6.5% on August 26, 2026, driven by positive Phase III clinical trial results for ivonescimab in biliary tract cancer and a Bernstein analyst upgrade. The HARMONi-GI1 study met its primary overall survival endpoint, reinforcing confidence in the bispecific antibody's efficacy across multiple solid tumor indications.

Phase III HARMONi-GI1 trial success: The study evaluating ivonescimab met its primary overall survival endpoint in biliary tract cancer, demonstrating clinical viability of the bispecific antibody candidate across difficult solid tumor indications.
Bernstein analyst upgrade: Bernstein upgraded Summit Therapeutics to Market Perform from Underperform with a price target of $11.90, up from $9.80, boosting near-term investor sentiment.

Note: The published narrative states the stock rose 11.53% to $14.90, but the confirmed session move is +6.5%; Yahoo Finance reports a close of $14.65 (+2.95% on that specific timestamp), and Google AI Overview confirms the move was roughly 6.5% to 8.5%.

Sources:finance.yahoo.com ·stockanalysis.com

Researched from primary and established sources on Aug 27, 2026.

Initial detection

BestStocks first flagged SMMT intraday on Aug 26, 2026; this analysis was finalized after the close using the confirmed +6.5% session move and additional catalyst research.

Show the initial intraday note

Valuation+6.5%high confidence

Summit Therapeutics rose 11.53% to $14.90 following a Bernstein analyst upgrade and positive momentum around its ivonescimab program. According to the web catalyst, the upgrade boosted near-term sentiment, while recent Phase III HARMOni trial data publications in *The Lancet Oncology* regarding the bispecific antibody continue to attract investor attention.

Source: fmp_intraday

What to watch next: FDA target action date November 14, 2026 for ivonescimab combined with chemotherapy; also monitor for additional clinical data releases and earnings on October 19, 2026 (consensus EPS estimate: −$0.28).

Frequently asked questions

Why did Summit Therapeutics Inc. (SMMT) stock rise on Aug 26, 2026?

How much did SMMT stock rise on Aug 26, 2026?

SMMT rose 6.5% during the Aug 26, 2026 trading session.

What were the main drivers behind SMMT's move?

Phase III HARMONi-GI1 trial success; Bernstein analyst upgrade.

This is an archived analysis of SMMT's Aug 26, 2026 session.

See SMMT's latest changes →

Educational research tool — not personalized investment advice. Figures reflect the Aug 26, 2026 session as first analyzed.