INBX CEO Keeps Buying as Short Sellers Hold Their Ground

Inhibrx Biosciences enters its November 13 earnings window with one of the more striking insider-buying patterns in the biotech space right now, set against a short position that remains stubbornly large and shows no sign of unwinding.

The most notable fact about this stock is what the CEO has been doing with his own money. Mark Lappe made multiple open-market purchases on October 14, none under a 10b5-1 plan, spending roughly $630,000 at prices around $84 to $86. That followed two more discretionary buys on September 25 and September 28 totalling nearly $675,000, again at market prices in the high $90s. Net across the past 90 days, Lappe has bought approximately 60,040 shares worth just over $6 million. He now holds 970,453 shares, or about 6.6% of the company. These are real-money, unscheduled transactions by the man running the business, at prices that are now comfortably below the current level of $95.66 after Tuesday's 8% single-day gain.

Short positioning tells the other side of the story. At 23.5% of the free float, the short interest is high by any standard. It has been remarkably stable: the share count has barely moved in 30 days, drifting only about 3.6% higher over that period, and the week saw a marginal 0.5% reduction. Importantly, the borrow market is not under stress. Cost to borrow has eased to 0.46%, down 8% on the week and 15% over the month. Availability is relaxed at 330%, meaning there are more than three shares available to lend for every one already borrowed. The ORTEX short score sits at 73.4, firmly elevated, but it has nudged lower from 74.2 two weeks ago. Shorts are committed, but there is no sign of forced covering or a squeeze building in the lending market. Options positioning reinforces the bullish lean: the put/call ratio is 0.19, well below its 20-day average of 0.21 and running near the lower end of the year's range, suggesting call demand continues to dominate.

The activist register adds another layer of complexity. Both Lappe and co-founder Jon Faiz Kayyem filed Schedule 13D/A positions in early 2026, the most activist-intent filing type in the SEC register. Perceptive Advisors and Viking Global each hold near 9.9% on passive 13G filings, and Schonfeld Strategic Advisors has a fresh 5.3% stake filed in August. Bank of America, notably, filed an updated 13G on October 28 showing its stake has dropped from 5.9% to 2.4%. As always, 13D/G positions are event-driven disclosures around the 5% threshold and stakes are as-last-disclosed, so current positions may differ. The concentration of specialist healthcare funds at the top of the register alongside a CEO actively adding to his own position draws a clear line: the informed money on both sides has strong views, and neither has moved much.

Analysts are broadly constructive but coverage is thin. HC Wainwright initiated with a Buy and a $245 target in August 2026. Stifel had already initiated Buy in April at $150. JMP Securities sits at Market Perform with no published target. With the stock at $95.66 and the mean target at $267, the stated upside looks extreme, though the analyst base is small and the initiations staggered across a wide price range. Valuation multiples are negative throughout, as expected for a pre-commercial biotech. The ORTEX short score rank in the 9th percentile of its sector is the most actionable factor here, confirming the stock is among the most heavily shorted names in biotechnology. Earnings history has been volatile: the two prints before the most recent one produced one-day moves of minus 8.9% and minus 7.9%. The August 21 print, by contrast, moved the stock up 5.8% on the day and 24.5% over the following five sessions.

Retail attention is elevated. ORTEX's Wikipedia-pageview-based attention tracker shows a z-score of 6.0 against the stock's own 90-day history, a reading from October 19 that suggests a meaningful spike in casual investor interest around the recent price action.

With earnings set for November 13, sixteen days out, the key tension to watch is whether the CEO's concentrated buying cluster and the specialist hedge fund ownership can hold up against the 23.5% short interest if the clinical update disappoints. The short interest is stable, not building, but it is large enough that any adverse print could accelerate covering from an uncomfortable position.