What happened: Xencor (XNCR) shares surged on Monday, October 26, 2026 after the biotech presented updated Phase 1 results for XmAb819, its experimental ENPP3 x CD3 bispecific T-cell engager, in patients with advanced clear cell renal cell carcinoma (ccRCC), the most common type of kidney cancer.
Benzinga had the stock up 26.2% at $31.77 in the morning,
CNBC's midday movers said it was up 20% at a 52-week high of $30, and an
MT Newswires midday report on Yahoo Finance put the gain at 18%, with volume above 6.8 million shares against a daily average of about 1.4 million.
The key facts from Xencor's press release (October 25, 2026):
Where the data came from. The results were presented in an oral session at the ESMO Congress 2026 in Madrid by Dr. Sumanta Pal of City of Hope, with a data cut of September 1, 2026.
The patients. The study enrolled 119 patients across 11 intravenous dose levels. The 68 patients in the three expansion cohorts were heavily pretreated, with a median of three prior lines of therapy, and all had received at least one PD-(L)1 inhibitor and at least one VEGFR TKI.
Response rates rose with dose. The confirmed objective response rate (cORR) was 30% at 100 mcg/kg (n=30), 44% at 200 mcg/kg (n=25) and 45.5% at 400 mcg/kg (n=11).
The chosen dose. Xencor selected 400 mcg/kg as its proposed recommended Phase 3 dose, citing the 45.5% cORR, a 55% unconfirmed response rate and an 82% six-month progression-free survival Kaplan-Meier estimate.
Next steps. Xencor said it plans to discuss a potential accelerated approval pathway with the FDA in key ccRCC subgroups in the first half of 2027 and plans a global randomized study of XmAb819 against tivozanib.
Cash runway. CNBC reported Xencor said its cash is sufficient to fund operations into 2029.Note the sample size: the 400 mcg/kg cohort had 11 evaluable patients, and the press release's 95% confidence interval for its response rate runs from 16.8% to 76.6%. Early-stage results can change with more patients and longer follow-up.
Educational content only, not financial advice. Options involve significant risk and are not suitable for every investor.
Why This Matters for Options Traders
1. Clinical data is a binary-style event, and IV usually falls once it is out. Before a scheduled data readout, small and mid-cap biotech options often carry elevated implied volatility (IV) because the stock can gap sharply either way. Once results are public, that event premium typically drains, the same pattern as IV crush after earnings. A trader who bought calls before the data could be right on direction and still see some of the gain offset by falling IV.
2. The move happened as a gap, not a trend. Xencor announced the data on Sunday, so the repricing came at Monday's open. Positions held over the weekend absorbed the whole move at once, with no chance to adjust. That is the core risk of holding short options into any biotech catalyst: a short call or short put can go from a small loss to a large one overnight.
3. A big move resets strikes and Greeks. After a 20%-plus jump, strikes that were out of the money on Friday may now be deep in the money, with deltas near 1 and little time value left. Traders rolling or adjusting positions are working with a different option chain than the one they opened.
4. Liquidity matters more in smaller names. Options on smaller biotech stocks often have wider bid-ask spreads and thinner open interest than large-cap options, especially in strikes far from the money. On a heavy-volume day, spreads can widen further, so the quoted mark may not be a price you can actually trade at.
5. The catalyst calendar does not end here. Xencor has pointed to FDA discussions in the first half of 2027 and a randomized study to come. Later-dated options may keep some premium for future news, while near-dated contracts mostly reflect day-to-day movement.
Common Ways Traders Think About This Setup (Educational)
Check where IV is now versus before the data. Comparing current implied volatility with its recent range shows how much event premium has already left the options.
Long premium after the event needs further movement. Buying calls or puts after a gap is a bet on the next leg, not the one that already happened.
Short premium needs defined risk. Selling options on a volatile biotech without a hedge exposes a trader to the next gap; vertical spreads cap the maximum loss.
Use limit orders. In wide markets, a limit near the midpoint helps avoid paying the full spread.
Size for small-sample risk. An 11-patient cohort is a thin base for a large valuation change, and follow-up data can move the stock either way.Key Takeaways
Xencor presented Phase 1 XmAb819 data in advanced clear cell kidney cancer at ESMO 2026, reporting a 45.5% confirmed response rate at its proposed 400 mcg/kg Phase 3 dose.
XNCR traded up roughly 18% to 26% on October 26, 2026, depending on the time of the quote, on volume several times its daily average.
Biotech data events tend to lift IV beforehand and crush it afterward, and the gap risk falls on anyone short options through the news.
Small sample sizes, wide option spreads and future catalysts (FDA talks in 1H 2027, a randomized study) all shape the risk from here.Sources
Business Wire: Xencor Presents Phase 1 Dose Selection Data for XmAb819 in Advanced Clear Cell Renal Cell Carcinoma (Oct. 25, 2026)
Xencor: Press releases
CNBC: Stocks making the biggest moves midday, Lockheed, JetBlue, CoreWeave, Surgery Partners and more (Oct. 26, 2026)
Benzinga: Range Resources, Xtend AI Robotics, Oruka Therapeutics and other big stocks moving higher on Monday (Oct. 26, 2026)
Yahoo Finance / MT Newswires: Top Midday Gainers (Oct. 26, 2026)
OCC: Characteristics and Risks of Standardized OptionsBy the OptionsPilot Editorial Team. Published October 26, 2026, 12:40 PM PT. This article is for education only and is not investment advice. Options involve risk and are not suitable for all investors.
