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Ultragenyx Pharmaceutical heads into its November 3 earnings with the gap between its short sellers and its options traders growing wider, not narrower.
The short interest story has changed materially since last week's note. Short interest is now running at 21.3% of the free float, up from 17.4% just a week ago, a 23.6% jump in shares borrowed in seven days and a 28.7% increase over the past month. This is no longer a gradual drift. Roughly 3.7 million additional shares were added to the short book between October 7 and October 8 alone, and the position has held at that elevated level through to October 13. The ORTEX short score has climbed to 58.3, its highest reading in the current history, having risen steadily from 54.9 at the start of the month. Yet the borrow market continues to offer no friction to short sellers. Cost to borrow is 0.48%, essentially unchanged on the week and down over the past month. Availability is ample at 750%, meaning there are more than seven shares available to lend for every one already borrowed. Even at the tightest point in the past year, availability only compressed to 705%. There is no mechanical pressure forcing short sellers to cover.
Options traders, by contrast, are positioned with striking conviction in the other direction. The put/call ratio has reached 0.30, the lowest reading of the past 52 weeks, against a 20-day mean of 0.40 and a z-score of minus 0.76. The direction of travel is even more striking than the absolute level: the PCR was above 1.9 in early September and has fallen in almost every session since, a sustained shift toward call-heavy positioning that has now touched its annual extreme. That is the same bullish tilt flagged in the prior note, but it has extended further rather than reverting.
The Street is divided in a way that maps cleanly onto this split. The bear case is concrete and well-articulated: GTX-102's Phase 3 ASPIRE failure eliminated what analysts had modelled as a major revenue driver, with roughly $1.7 billion in peak revenue estimates stripped out and FY30 non-GAAP net income forecasts cut to $66 million. Goldman Sachs cut its target to $19 from $28 in early September, maintaining Neutral. JP Morgan downgraded to Neutral and cut its target from $80 to $36 on the same day, the most dramatic single revision in the recent history. The bull case rests on a different calculation: probability of success on a remaining asset has been raised to 100%, the company now holds two priority review vouchers that could collectively generate around $400 million in non-dilutive capital, and the commercial franchise is argued to be materially undervalued on its own before any pipeline credit. Evercore, Barclays, Morgan Stanley, Citi and Canaccord all raised targets in the week following Goldman's cut, a notably constructive response to what had appeared to be a capitulation moment. The mean analyst target of $28 compares to a current price of $14.92, implying significant implied upside, though that gap reflects the range of conviction rather than consensus confidence.
Institutional positioning adds one further data point worth noting. BlackRock lifted its stake to 10.8% as of September 30, adding 3.35 million shares. State Street also added 1.4 million shares in the same period. These are passive and index-related flows in part, but the scale of BlackRock's purchase in a single quarter is not trivial relative to the float. FMR, on the other hand, cut its disclosed position from 8.3% to 3.5% earlier in the year, a meaningful reduction that reinforces how differently large institutions have read the same fundamental picture. Insider activity has been modest and almost entirely under 10b5-1 plans, most notably the CFO selling in July and August at prices well above current levels.
With earnings due November 3, twenty days away, the question the market is left sitting with is whether the call-heavy options book anticipates a positive catalyst or simply reflects retail attention. Retail engagement on the stock, as measured by Wikipedia page views and ORTEX stock page visits, spiked to a z-score of 3.3 in late September, an unusually high reading relative to the prior 90 days. Whether that attention translates into informed positioning or noise is precisely what the earnings print and any pipeline update between now and then will clarify.
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