OPKO Health shorts build at fastest pace in a year, eight days before earnings

Short interest in OPK jumped 11.8% last week to 5.1% of free float, its highest level in at least a year. That weekly move is 3.1 standard deviations above the company's typical weekly change, making it one of the sharper short-interest builds the stock has seen.

A week of conflicting signals

The short build arrived in the same window as two bullish analyst moves. Barrington Research upgraded OPK to Outperform on 16 October, reversing its April downgrade. Piper Sandler raised its price target from $3.00 to $4.00 the same day, reiterating Overweight. The consensus now sits at buy, with a mean price target of $4.15 against a close of $1.61.

The stock rose 16.7% over the past week. Its closest peers moved a median of -0.4% in the same period. That divergence is sharp, and it appears to have attracted short sellers rather than deterred them: 38.9 million shares are now short, up from roughly 34.9 million a week ago.

The options market added a further note of caution. On 16 October the put-call ratio reached 0.0523, close to its 52-week high of 0.069. By 19 October it had pulled back to 0.0363, 1.9 standard deviations below the 20-day mean, as call positioning reasserted itself. The direction of travel in the options market is now unclear: one day's sharp put-buying followed by a rapid reversal tells you traders are positioning actively, not holding a settled view.

Lending market stays loose

Despite the short-interest build, the borrow market is not strained. Availability stands at 341%, meaning roughly three and a half shares are available to borrow for every share already borrowed. That is well above the 52-week trough of 286%. Cost to borrow is 0.50% annually, low by any standard, and has fallen about 11% over the past month even as short interest climbed.

That combination, rising short interest alongside ample and cheap supply of borrows, points to straightforward directional positioning rather than a technical squeeze. There is no scarcity of shares to borrow at these levels.

What the bull and bear cases say

The bull case rests on the $722m sale of BioReference to LabCorp, which simplified the balance sheet and funded a cash cushion of $314.4m at end of Q2. The ModeX pipeline carries several near-term clinical catalysts. The bear case points to a Q1 miss on both revenue ($124.2m) and EPS (-$0.07), a narrow margin between cash and debt, and a guidance range that management itself flagged as dependent on a sharp second-half recovery.

CEO and Chairman Phillip Frost, as last disclosed the holder of a 34.1% stake on a Schedule 13D/A filed in July 2026, has been buying in the open market, though the most recent cluster of purchases on record dates to November 2025. Schedule 13D/G positions reflect the stake as last disclosed and may not capture subsequent changes.

Earnings are due on 28 October. The last two prints produced one-day moves of 10.1% and 35.2% respectively. The EPS momentum factor score sits at the 97th percentile over the past 30 days. Whether that momentum reflects genuine estimate revision or simply the low base of prior misses is the question the print will answer.

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Watch: the short interest level going into 28 October and whether the borrow market tightens as the earnings date approaches.