ArriVent Shares Fall 27% on Monday, the Day Early ARR-217 Trial Data Were Filed

ArriVent BioPharma (Nasdaq: AVBP) shares fell 26.9% on Monday, Oct. 26, closing at $15.36 from $21.00 on about five times their normal volume. The S&P 500 ETF (SPY) rose 0.71% that session. The stock fell on the day the company filed initial Phase 1 data on its ARR-217 cancer drug in an 8-K, which was accepted at 6:00 a.m. ET. Neither the filing nor the press release attached to it says why the shares fell.

Response rates in colorectal cancer

The press release, dated Oct. 25, reported a 44.8% objective response rate (13 of 29 patients) at the 6 mg/kg dose in late-line colorectal cancer patients, with a 93.1% disease control rate at that dose. Across doses of 4 mg/kg and higher, the objective response rate was 34.2% (25 of 73). The data cover 123 heavily pretreated gastrointestinal cancer patients as of an Aug. 5, 2026 cutoff. The results were presented as an oral presentation at the ESMO Congress 2026.

Safety profile

The company said ARR-217 was generally well tolerated. Across all doses, 30.1% of patients (37 of 123) had Grade 3 or higher treatment-related adverse events, including neutropenia at 12.2% and diarrhea at 8.9%. At 6 mg/kg, the Grade 3 or higher rate was 20.4% (10 of 49). The company reported no Grade 5 treatment-related adverse events and no interstitial lung disease.

Cash and losses

ArriVent said ARR-217 has moved into a Phase 1b dose optimization study at 5 and 6 mg/kg, with further data expected in 2027. Losses have grown. The net loss for the year ended Dec. 31, 2025 was $166.3 million, against $80.5 million a year earlier, and the net loss for the quarter ended June 30, 2026 was $49.9 million, against $31.4 million a year earlier. Diluted loss per share for that quarter was $1.05, compared with $0.90. The company had $154.7 million in cash and equivalents as of June 30, 2026. Before the move, the stock's market value was about $1.04 billion.