PACB shares closed Tuesday at $1.83, up 7% on the day and 24.5% on the week, a move that stands well clear of every correlated peer and puts the squeeze firmly on a short book that was already unwinding.
The short-side retreat is the clearest signal this week. Short interest has fallen 5.8% over seven days to 15.3% of the free float, roughly 46.3 million shares, continuing a decline from a peak of around 51.4 million shares in early September. That month-long unwind of 7.5% in SI percentage terms coincides almost exactly with the stock's 30.7% gain over the same period. The borrow market has followed suit: cost to borrow has collapsed from above 0.8% in mid-September to just 0.26% now, down 54% on the week and 61% over the month. Availability has loosened sharply too, reaching 325%, meaning there are more than three shares available to borrow for every one already shorted. That is the loosest the lending pool has been all year, a far cry from the 52-week tightest reading of 55.6%. With days-to-cover at 10.5 per the most recent FINRA fortnightly figure, covering pressure is real but easing fast. The ORTEX short score has also dropped, from 71.6 last Monday to 66.1 today, still elevated in absolute terms but moving in the right direction for longs.
Options traders are not amplifying the bullish momentum. The put/call ratio is at 0.12, just below its 20-day average of 0.12 and sitting half a standard deviation under the mean. There is no aggressive call buying chasing the move, but equally no defensive hedging building. The 52-week range on the PCR runs from 0.08 to 0.20, and the current reading near the lower end of that range is consistent with a modestly call-leaning book rather than a speculative surge. The market is not piling in.
The Street is cautious and the data backs the caution. The consensus is hold, with UBS the most recent mover, lowering its target to $1.35 from $1.50 on September 9 while assuming coverage at Neutral. Barclays has kept an Underweight rating all year, raising its target to $1.50 in May after cutting it to $1.00 in April. The mean analyst target is $2.16, roughly 18% above the current price, but with all analysts clustered at hold or underweight except Stephens, the upside call is thin. Valuation multiples offer little comfort: PE, PB and EV/EBITDA are all deeply negative, reflecting a company still burning cash. The ORTEX factor scores reinforce the picture, with EPS momentum in the 23rd percentile over 30 days and the 30th over 90 days, and a short score rank in just the 16th percentile, signalling that the short-interest overhang remains high relative to the broader universe even as it unwinds. The bull case rests on consumables revenue mix improving gross margins and Revio platform utilization hitting post-launch highs. Bears point to instrument demand weakness, margin pressure, and continued softness in China.
The institutional register is worth a glance given the week's move. BlackRock added 7.1 million shares as of end-August, bringing its stake to 10.4%. ARK Investment Management holds 9.6% and added modestly. SoftBank sits at 6.6% but has not changed its position since June. On the activist register, there are no Schedule 13D filings, all holders are passive 13G filers. ARK's latest amendment, filed August 14, shows its stake trimmed from 12.3% to 9.6%, a reduction of more than 20% in percentage terms. Millennium, which once held 6%, has filed down to 0.7% as of April 2025. Stakes are as-last-disclosed around the 5% threshold; holders dropping below may exit without further filing.
Recent earnings history gives the bear camp its clearest ammunition. PACB fell 8.8% the day after its August 2026 print and a further 11.5% over five days. The prior event, reported in early August 2026, produced a 19.1% single-day drop and a 22.9% five-day loss. The next earnings date is November 5. With the stock up 25% in a week and short interest still running above 15% of the float, how the company frames instrument demand and margin trajectory in that November print becomes the central question between now and then.
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