Guselkumab's numbers in an Asian population, from a dedicated phase 4 trial

Design

phase 4 randomised, double-blind, placebo-controlled trial with crossover at week 16, reported September 2025

Population

327 Chinese adults with moderate-to-severe plaque psoriasis, mean age 41.5 years, 79.2% men

Primary outcome

co-primary PASI 90 and Investigator's Global Assessment 0/1 at week 16

Effect

PASI 90 82.4% versus 2.0% and IGA 0/1 88.8% versus 7.1% at week 16 (both p<0.001); PASI 90 79.2% at week 48

Most biologic evidence in psoriasis comes from predominantly white trial populations, and the question of whether it transfers gets asked in every Indian clinic. This phase 4 randomised, double-blind, placebo-controlled trial, reported in September 2025, enrolled 327 Chinese adults with moderate-to-severe plaque psoriasis and randomised them 2:1 to guselkumab 100 mg at weeks 0 and 4 then eight-weekly, or placebo to week 12 with crossover at week 16.

At week 16, 82.4% on guselkumab reached PASI 90 against 2.0% on placebo, and 88.8% reached an Investigator's Global Assessment of 0 or 1 against 7.1%, both p<0.001. Responses held at week 48 (PASI 90 79.2%) and the crossover group caught up (80.2%). Adverse events over the first 16 weeks were comparable between arms at 41.9% and 39.1%, and serious adverse events were uncommon.

The caveats are ordinary rather than damning: 79.2% of participants were men, the comparator was placebo rather than another biologic, and a single-country trial does not settle the question for South Asian skin specifically. But a PASI 90 rate above 80% in an Asian population, sustained to a year, is close to what the global programme reported, and that is the useful information. Where a patient asks whether these figures apply to them, the answer is now better supported than an extrapolation. Cost remains the binding constraint in India, and biosimilar availability, not efficacy, will usually decide.

• Set PASI 90, not PASI 75, as the target when discussing what good control looks like
• Quote a maintained response: roughly four in five still at PASI 90 at week 48
• Delayed starters caught up by week 48, which is worth saying to a patient facing a funding wait
• The trial was 79% male and single-country — do not over-extrapolate to South Asian women
• Access and cost, not efficacy, decide biologic choice for most Indian patients; address that first

The statistics, in plain English

An 82.4% versus 2.0% difference at week 16 is so large that the p-value adds nothing — the comparison is against placebo, not against another active drug, so it measures whether guselkumab works, not whether it works better than an alternative. Week 48 figures come from an open-label continuation in which everyone is on drug, so they describe persistence of response rather than a randomised comparison. Serious adverse events of 0.9% against 5.5% run in guselkumab's favour but rest on very few events in a 16-week window, and should not be read as a safety advantage.

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