ZYME Shorts Build as Earnings Loom Nine Days Out

Zymeworks heads into its November 6 earnings print with short sellers quietly adding exposure and options traders growing noticeably more comfortable, a split in sentiment that makes the setup more interesting than either signal alone would suggest.

Short interest has climbed in a way that deserves attention. It now stands at 7.5% of the free float, up 8.3% over the past week and nearly 20% higher than a month ago. The move is steady rather than dramatic, but the direction is consistent: bears have been adding through most of October. FINRA's fortnightly official count, settled through October 15, puts short shares at 5.58 million with 4.4 days to cover, broadly confirming the trend. What makes the positioning less alarming is the borrow market itself. Cost to borrow is just 0.53%, near the low end of its 30-day range. Availability, at 793% of outstanding short interest, is generous by any measure, nowhere near the 367% floor seen earlier in the year. There is plenty of room for new shorts to enter without a squeeze dynamic forming.

Options tell the opposite story. The put/call ratio has dropped sharply from recent extremes, falling from a 52-week high of 2.56 in mid-October to 1.53 now. That reading is 1.3 standard deviations below its 20-day average of 2.03, meaning call volume has been gaining ground on puts for two straight weeks. The shift lines up almost exactly with the stock's 7.2% gain on the week and a 9% rise over the past month. Traders who were heavily hedged are pulling back those defensive positions as the stock moves higher.

The Street is firmly in the bull camp. The analyst consensus carries a mean price target of $41.43 against a current price of $28.85, implying roughly 44% upside. All recent coverage actions have been positive: Truist raised its target to $34 from $32 earlier this month, Citigroup moved to $39 in late September, and Wolfe Research initiated with an Outperform rating in mid-September. JP Morgan had raised to $33 from $31 in early September. The bull case centres on zanidatamab's FDA-approved status in first-line HER2-positive gastric cancer, tiered royalties that step up to 20% above $2 billion in annual net sales, a $572.5 million pro-forma cash position, and a $100 million milestone expected from the Theravance acquisition in early 2027. Bears counter that the stock's value is heavily concentrated in a single commercial outcome, assign only a 10% probability to royalty streams from bile tract cancer and gastric cancer, and flag pipeline risk in ZW191 and ZW251. The EV/EBITDA multiple has compressed by roughly 1.1 turns over the past 30 days even as the price has risen, reflecting improving earnings power rather than multiple expansion.

One ownership fact stands out. EcoR1 Capital holds a 13D activist position at 30.7% of the class, seven filings since December 2024, with no reduction disclosed as of November last year. That is a dominant anchor position. Rubric Capital is the next largest at 9.5% of shares, having grown its stake from 7.7%. Perceptive Advisors holds 5.4%, filed in April. Stakes are as last disclosed around the 5% threshold, and holders dropping below that level may not file again, but the concentration of ownership here is notable: EcoR1's disclosed stake alone represents a substantial share of all shares outstanding. The institutional count of 163 holders is consistent with a mid-cap clinical-stage biotech. One signal worth flagging separately: Wikipedia traffic for Zymeworks is running more than two standard deviations above its own 90-day average, according to the ORTEX alt-data layer, the highest retail attention reading for the stock in the observed window.

The earnings record is mixed but skewed positive. The May 2026 print produced a 13.5% one-day decline. The August event, however, delivered a 4.5% gain on the day and a further 8.6% over the following five sessions. The next event is nine days away, on November 6, and with short interest building and options traders simultaneously rotating toward calls, the question heading in is whether the commercial narrative around zanidatamab's launch trajectory can justify a stock that has already moved 8.8% higher over the past month.