XBI has gained 5.2% this week, and the borrow market that was at crisis tightness just days ago has meaningfully loosened — the two moves together tell a coherent story about shorts under pressure.
The lending market shift is the most notable development since last week's note. On May 19-20, availability had collapsed to 0% — every share in the lending pool was lent out, the tightest reading in the 52-week window. That has since eased materially. Availability recovered to 10.6% by May 26, with brief spikes back toward 21% mid-week. Cost to borrow has followed the same path: after hitting 4.62% on May 19, CTB dropped sharply to 2.10% by May 26 — a fall of more than half in seven days. The borrow market is still tight by historical standards, but the acute squeeze pressure that defined the prior week has abated.
Short interest tells a steadier story. Shares short remain essentially flat on the week, down just 0.04% to 113% of float. That figure remains structurally elevated — though as noted previously, ETF mechanics allow short interest to exceed 100% through creation/redemption dynamics, so the absolute level alone doesn't signal distress. The more meaningful observation is that shorts have not covered in any material way despite the 5% price rally. The ORTEX short score holds near 79, well into elevated territory, suggesting the structural bear position in biotech remains intact even as the price moves against it.
Options positioning has been unwinding its defensive posture. The put/call ratio has drifted down to 1.42 — nearly 1.5 standard deviations below its 20-day average of 1.54. That is a notable shift from the defensive hedging that dominated options flow through late April and early May, when the PCR touched 2.43 at its 52-week high. The direction of travel is clear: options traders are shedding puts relative to calls as the ETF climbs. The PCR's 52-week low of 0.91 shows there is still considerable room further in that direction if sentiment continues to improve.
The combination of easing borrow costs, recovering availability, and a declining PCR in the face of a 5% weekly gain paints a picture of short-side stress rather than conviction. Shorts have held their position by share count, but the cost of maintaining those positions fell this week as more inventory re-entered the lending pool. Whether that inventory relief persists — or whether availability tightens again as the ETF continues to attract bearish flow — is the key tension to watch heading into the coming sessions.
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