Why Connect Biopharma stock sank on its asthma data and rallied on its COPD data

Connect Biopharma (Nasdaq: CNTB) reported two Phase 2 readouts for rademikibart two weeks apart, and its stock went in opposite directions on them. The asthma study, released at 7:00 a.m. ET on September 15, 2026 under a headline calling the data positive, missed its primary endpoint with p=0.153, and CNTB fell from 1.8505 to 0.9491 in the first 15 minutes of pre-market trading, a drop of 48.71%. The COPD study, released at the same time on September 30, met its primary endpoint with an 81% reduction in treatment failure against placebo (p=0.0122), and CNTB rose from 1.00 to 1.19 over the same 15 minutes, a gain of 19.00%.

Two trials built the same way

Both studies carry the Seabreeze STAT name and test a single subcutaneous dose of rademikibart added to standard care in patients who arrive with an acute flare and type 2 inflammation, defined as at least 300 eosinophils per microliter of blood. Both measured the rate of treatment failure over about four weeks as the primary endpoint, which is why the results can be read side by side.

Why a 66% reduction was not enough in asthma

The asthma release attributed the miss to an overall treatment failure rate lower than the trial had projected. A trial is sized around an expected number of events, and when fewer patients in either arm fail than planned, even a large relative reduction can be indistinguishable from chance because the comparison rests on fewer events than the design assumed. With 79 patients on rademikibart and 81 on placebo, the 66% reduction produced p=0.153, well above the conventional 0.05 threshold. The study did meet a lung-function measure: forced expiratory volume in one second (FEV1) rose by 250 mL on rademikibart against 120 mL on placebo by Day 7, a 130 mL difference with p=0.023.

What the COPD study added

In COPD the primary endpoint and two key secondary measures cleared significance. Besides the 81% cut in treatment failure, rademikibart reduced new moderate-to-severe exacerbations by 85% through Week 4 (p=0.030) and reduced emergency department visits and hospital admissions for new exacerbations by 100% (p=0.0137). Lung function was the measure that missed this time, with a 70 mL advantage at Week 4 and p=0.1607, the reverse of the asthma pattern. Connect said it plans to seek alignment with the FDA on a Phase 3 program.

The CNTB reaction, measured

Both releases crossed at 7:00:02 a.m. ET, two and a half hours before the regular session. After the asthma release CNTB traded at 1.7380 one minute later, down 6.08%, and stayed near that level for about eight minutes before the selling began; our 10-minute reading was 1.2944, down 30.05%, and the 15th one-minute bar on the chart closed at 0.9491, down 48.71%.

CNTB had not recovered by the second readout: it stood at 1.00 when the COPD release crossed on September 30, 45.96% below its level before the asthma data. The first minute after the COPD release printed 1.0295, up 2.95%; the 10-minute reading was 1.08, up 8.00%, and the chart's 15th bar closed at 1.19, up 19.00%. Even after that gain the stock was 35.69% below where it had been before September 15.