ONCO Short Interest Collapses 75% in One Week

Key takeaway: ONCO short sellers fled en masse this week, cutting positions by 75% to just 5.7% of float after shares crashed 80% in the past month. Cost to borrow remains extreme at 353% despite the unwind. HRT Financial, a 10% owner, sold over 197,000 shares in four days.

Price action & positioning

ONCO closed at $0.59 on April 24, down 12% on the day. The stock fell 21% over the past week and has plunged 80% in one month. The biotechnology micro-cap trades near multi-year lows with negligible market capitalization.

Short interest & lending

Short interest collapsed to 88,448 shares on April 23, down 75% from the prior week. SI now represents just 5.7% of free float, half the level seen a month ago. The sharp decline followed a period of extreme volatility in mid-April when short shares spiked above 1.6 million on April 13 — the highest in the 30-day window. Since then, shorts have unwound aggressively.

Days to cover sits at 96th percentile, suggesting low liquidity amplifies any position changes. Utilisation dropped to 15.5% from 19% a week earlier, well below the 52-week high of 98.6% reached in late March. Shares available to borrow have loosened considerably.

Cost to borrow remains punishing at 353%, though down 29% week-over-week. CTB peaked above 680% in early April and has trended lower alongside the SI unwind. The current level is still more than ten times March's baseline of 33%, reflecting the stock's extreme volatility and risk profile.

Institutional positioning

Altos Venture AG holds the largest institutional stake at 54,646 shares, representing 7.9% of the company. That position has not changed since December. Named individuals Ralph Schiess and Christian Bruhlmann each own roughly 1,400–1,600 shares, with minimal recent activity.

DRW Holdings trimmed its position by 4,547 shares to 7,809 as of year-end. Geode Capital added 1,680 shares in late February, bringing its stake to 2,340. XTX Markets initiated a 2,165-share position in the fourth quarter.

Insider activity

HRT Financial LP, classified as a 10% owner, sold heavily over four consecutive trading days in mid-April. The firm offloaded 198,039 shares for $144,469 between April 14 and April 21. Net insider activity over 90 days shows a positive 399,579 shares valued at $297,344, driven by executive equity awards granted in December 2024 at zero cost.

Chief-level officers received 177,462-share awards each on December 20, accounting for the bulk of insider inflows. HRT's April selling spree offset part of that total in dollar terms.

Valuation & factor positioning

Enterprise value is negative at -$4.9 million as of fiscal year-end 2027. The company carries more cash than debt and equity value combined, typical of pre-revenue biotechs burning capital.

Factor scores show ONCO ranking at the 15th percentile for short score and 96th percentile for days to cover. The dividend score sits at 32, sector score at 79, and utilisation rank at 46th percentile. Earnings yield and EV/EBIT multiples are unavailable.

What to watch

ONCO reports earnings on May 14 at 8:00 PM UTC. The prior earnings event on March 25 was announced with significant lead time in November 2025. Investors will look for updates on clinical pipeline progress and cash runway.