Design: Randomised, double-blind switching study
Population: 453 adults with plaque psoriasis responding to reference ustekinumab
Primary outcome: AUCtau and Cmax, weeks 52–64
Effect: GMR AUC 0.93 (90% CI 0.89–0.98); Cmax 0.95 (0.90–1.00)

This double-blind trial enrolled 494 adults with moderate-to-severe plaque psoriasis on reference ustekinumab. At week 28, 453 responders were randomised to continue the reference product or to switch three times, alternating with the biosimilar ABP 654 at weeks 28, 40 and 52. It was published in the British Journal of Dermatology in September.

Between weeks 52 and 64, geometric mean ratios were 0.93 (90% CI 0.89 to 0.98) for AUC and 0.95 (0.90 to 1.00) for Cmax, within the 0.8 to 1.25 equivalence margin. PASI response, antidrug antibodies and adverse events were similar.

This is the design regulators use to support interchangeability, meaning substitution without the prescriber's intervention. For prescribers, it supports switching stable patients to the biosimilar without expecting loss of response or more immunogenicity.

Switching a stable patient to ABP 654 is supported by pharmacokinetic and clinical equivalence.
Record the brand and batch at each switch for pharmacovigilance.
Tell patients the evidence: equivalent levels, response and antibody rates.
Check local availability and formulary status before switching.

Why it matters

It gives trial evidence that repeated back-and-forth switching does not provoke immunogenicity.

The statistics, in plain English

Equivalence is shown when the 90% confidence interval of the exposure ratio sits within 0.8 to 1.25; both did. Efficacy and immunogenicity were secondary end points, so 'similar' there is reassurance rather than formal proof.