PBM heads into mid-May in one of the stranger post-squeeze configurations in the small-cap biotech space: short interest has collapsed back to normal levels, yet the cost to borrow remains at a near-record 324%.
The backstory starts in mid-April. A US executive order signalling plans to evaluate ibogaine's therapeutic potential landed on April 17. PBM — which builds GMP-grade ibogaine supply chains and is running a Phase IIb trial — became the obvious trade. Short interest rocketed from around 2.5% of the free float to over 30% in just four trading sessions, as bearish traders bet the pop would fade. The stock had other ideas. It surged anyway, and the squeeze that followed was brutal. By April 30, short interest had collapsed 98.6% in a single week to under 0.4% of the float. The stock closed at $5.57 on May 12, still up 109% on the month.
The positioning picture now contains a striking split. Short interest has largely normalised — sitting at just 2.1% of the free float, with shares short at roughly 47,000, barely above April's pre-catalyst lows. Availability is no longer a constraint; borrow is freely available relative to the tiny residual short position. But the cost to borrow tells a completely different story. CTB peaked near 630% in late April and has only crawled down to 324% — still roughly ten times what it was before the catalyst hit. Lenders clearly haven't reduced their rates in line with the unwinding of shorts. That gap between near-normal short interest and near-record borrow cost is unusual and suggests the lending market is pricing in ongoing volatility risk even as the crowded short has dispersed.
The ORTEX short score of 46.7 is mid-range and has been largely stable over the past two weeks, consistent with a stock where the acute squeeze dynamic has passed but residual borrow friction remains. The days-to-cover rank sits at the 96th percentile — reflecting the thin float and low share count rather than an aggressive new short position being built. Institutional coverage is skeletal: Parallel Advisors holds 6.6% of shares, having added aggressively in Q1 2026, while KAOS Capital and Jeffrey Weiner make up most of the rest of the visible float. With total reported institutional holders numbering just eight, even small position changes move the needle materially.
Earnings history is worth noting here. The three most recent prints all delivered negative price reactions — down 3%, down 47%, and down 9% on the day. The 47% drop came in November 2025, one of the sharpest single-day earnings moves in the dataset. The next event is pencilled for June 25. That gives the stock roughly six weeks in which the dominant narrative will be clinical trial progress — specifically whether the Phase IIb trial dosing announcement from April 23 produces further operational updates — rather than financial results.
The peer group offers limited guidance. MCRB and TPST on Nasdaq are both up on the week, though correlation to PBM is modest. The ibogaine policy angle is specific enough that broad biotech peer moves carry little explanatory power here.
What to watch: whether the cost to borrow continues its slow bleed downward toward pre-catalyst levels — or stabilises well above them — will indicate whether the lending market views the current price as a settled equilibrium or a second catalyst setup still in progress.
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