AI Infrastructure, Biotech and Semiconductors Lead Today's Stock Gainers · Aug 17, 2026

Which US stocks moved most on August 17, 2026, the themes that drove them, and the news behind each move.

1. Market at a glance

- S&P 500 (SPY) 772.66 ▼ −0.0% - Nasdaq 100 (QQQ) 729.87 ▲ +1.2% - Russell 2000 (IWM) 304.04 ▲ +1.4% - Dow (DIA) 534.22 ▼ −0.9%

2. Biggest movers, grouped by what drove them

🤖 AI Infrastructure — Cerebras surged on expanding OpenAI partnership opportunities as AI market accelerates. - CBRS +15.1% — Cerebras Systems Inc. - SMTC +9.9% — Semtech Corporation 💊 Biotech — Argenx jumped on Phase 3 trial success for autoimmune myositis, expanding blockbuster drug potential. - ARGX +16.0% — argenx SE - NBTX +9.8% — Nanobiotix S.A. - MESO +9.1% — Mesoblast Limited - PGEN +7.4% — Precigen, Inc. - DFTX +6.2% — Definium Therapeutics, Inc. - OCUL +6.1% — Ocular Therapeutix, Inc. 🔌 Semiconductors — AXT surged on record indium phosphide demand driving optical component prices higher. - AXTI +17.6% — AXT, Inc. - SNDK +8.9% — Sandisk Corporation - CRDO +8.8% — Credo Technology Group Holding Ltd - AEHR +8.6% — Aehr Test Systems, Inc. - COHR +7.7% — Coherent Corp. - ACMR +6.5% — ACM Research, Inc. - VIAV +6.2% — Viavi Solutions Inc. 📡 AI Platforms — Rumble rallied on $3B AI compute opportunity from expanding power infrastructure. - FIGR +13.8% — Figure Technology Solutions, Inc. - RUM +10.5% — RUM Group Inc. 🏨 Hospitality & Travel — H World Group rose after Q2 earnings beat and new shareholder return plan announcement. - HTHT +11.3% — H World Group Limited - AIR +5.8% — AAR Corp. 📈 Low-Priced Small Caps — No news attached — a flow move, not a catalyst. - ALM +8.4% — Almonty Industries Inc. - VICR +8.0% — Vicor Corporation - PTEN +7.4% — Patterson-UTI Energy, Inc. - LUNR +7.2% — Intuitive Machines, Inc. - FIX +6.1% — Comfort Systems USA, Inc. - TER +5.8% — Teradyne, Inc. - CECO +5.7% — CECO Environmental Corp.

3. What drove the upside

- Cerebras Shares Jump 15% as Wedbush Flags Bigger OpenAI Deal Opportunity - argenx Phase 3 ALKIVIA Trial Meets Primary Endpoint in Autoimmune Myositis - AXTI Q2 Earnings Beat on Record InP Demand, Revenues Rise Y/Y - Rumble Eyes $3B AI Compute Run Rate From 250MW Power Pipeline

4. What weighed on it

- STUB −11.9% — StubHub Holdings, Inc. - LFTO −9.6% — Liftoff Mobile, Inc. - One group moved with no news attached — flow, not a catalyst.

5. How this was built

Warrants and leveraged ETFs were removed before grouping — they crowd out the underlying names they track. 50 tickers survived that filter. Every number here comes from market data. The theme names and the one-line explanations are written from the day's headlines — where a group moved with no headline behind it, we say so rather than inventing a reason. This is an observation of what moved, not advice and not a recommendation. This tells you where attention went today; it does not tell you what happens next.