Three distinct signals are converging on XBI simultaneously. The biotech ETF's lending market is at its tightest in months. Cost to borrow has surged 71% in a week. And options traders are pulling back on puts at an unusual rate.
The standout number is stark. Availability has dropped to 0% — every share in the lending pool is currently lent out.
One week ago, availability stood at 1.56%. A month ago, it sat above 30%. That collapse is now the tightest reading in the 52-week window tracked by ORTEX.
Cost to borrow reflects the pressure. CTB hit 4.62% on May 19, up from 2.70% a week prior. That's a 71% surge in seven days. The one-month move is even sharper — up 85% from the ~2.49% level at end-April.
Short interest sits at 113.2% of float. That figure reflects the nature of ETF mechanics — creation/redemption baskets can push short interest above 100% — but the direction matters. Shares short have crept up 0.46% over the past week and nearly 2% over the past month before a slight pullback.
While the lending market tells a bearish structural story, options positioning is moving in the opposite direction.
The put/call ratio for XBI stands at 1.44 — down from a 20-day mean of 1.57. That's 2.15 standard deviations below the norm. Yesterday's intraday reading hit 1.37, nearly 4 standard deviations below the mean.
For context, the 52-week range runs from 0.91 to 2.44. The ETF spent most of April in the 2.0–2.4 range — pure defensive positioning. The shift toward the lower end over the past two weeks represents a meaningful rotation away from put protection.
The ORTEX short score sits at 79.1 out of 100 — a reading that has held remarkably steady all month. It peaked at 79.4 on May 14 and has barely moved since. High short scores reflect the combined weight of the lending data: tight availability, elevated CTB, and elevated short interest as a percentage of float all feed into this composite.
What to watch: Whether CTB continues climbing from here. With availability at zero and short interest unchanged, any incremental demand to borrow creates immediate upward pressure on borrowing costs — and tighter conditions for existing short holders to maintain positions.
See the live data behind this article on ORTEX.
Open XBI on ORTEX →ORTEX Market Intelligence content is generated by AI from a snapshot of ORTEX's proprietary data. Content is informational only and does not constitute investment advice.
