Journal Publication

Firsekibart's solution formulation matches lyophilized version on bioequivalence

A 181-person trial in healthy Chinese adults found the subcutaneous solution and lyophilized powder forms of firsekibart met standard PK bioequivalence bounds with comparable safety.

A randomized, double-blind, single-dose, parallel-group trial in 181 healthy Chinese adults found firsekibart solution for injection bioequivalent to firsekibart lyophilized powder for solution.

By AppliedXLJuly 20, 2026

Executive Summary

A randomized, double-blind, single-dose, parallel-group study compared two subcutaneous formulations of the same drug, firsekibart, on pharmacokinetic exposure rather than clinical efficacy.
The new solution formulation matched the established lyophilized powder formulation on exposure, meeting the standard regulatory bioequivalence threshold on all three primary measures.
Adverse events were mild to moderate and comparable between the two formulations, with none classified as treatment-related and serious.
Because bioequivalence was demonstrated, the solution formulation can be expected to behave like the lyophilized formulation once used in patients, without requiring a fresh efficacy trial.

The question

Firsekibart already exists as a lyophilized powder for solution that is reconstituted before subcutaneous injection. This study asked whether a ready-to-use solution formulation of the same drug delivers the same systemic exposure, the pharmacokinetic question that determines whether a new formulation can be treated as interchangeable with an established one without repeating clinical efficacy trials. Bioequivalence

How it was done

The study was a randomized, double-blind, single-dose, parallel-group trial in healthy Chinese adult males. Participants received a single 200 mg subcutaneous dose of either the solution formulation (test, T, n=90) or the lyophilized powder formulation (reference, R, n=91), for a total of 181 participants, and were followed through Day 141. The primary objective was pharmacokinetic bioequivalence, concluded if the least-squares geometric mean ratios (GMRs) for maximum serum concentration and area under the concentration-time curve fell within 90% confidence intervals of 80.00% to 125.00%, the standard regulatory bioequivalence window. Safety was a secondary measure. Bioequivalence

The result

All three primary PK measures met the bioequivalence criterion. The T/R geometric mean ratio for maximum serum concentration was 104.26% (90% CI, 98.11% to 110.80%); for area under the curve to the last quantifiable concentration, 103.45% (90% CI, 98.15% to 109.04%); and for area under the curve to infinity, 102.14% (90% CI, 96.75% to 107.83%). Each ratio and its full confidence interval sat inside the 80.00% to 125.00% bound, the threshold that defines bioequivalence. Bioequivalence

Safety profile

Most treatment-emergent adverse events were mild or moderate and occurred at comparable rates between the two formulations. No treatment-related serious adverse events were reported in either arm, and the study identified no new safety signal for the solution formulation relative to the established lyophilized product. Bioequivalence

What it means for practice

Because the solution formulation reproduced the reference product's exposure profile within the standard bioequivalence bounds, the two formulations can be expected to perform the same way in patients despite the change in how the drug is prepared before injection. A ready-to-use solution removes the reconstitution step required for a lyophilized powder, a practical difference in administration rather than a change in the drug's biological activity, since the exposure data support treating the two as pharmacokinetically interchangeable. Bioequivalence

This analysis was produced using AI-assisted reporting systems, AppliedXL data, and official public records. These systems undergo editorial review, quality checks, and regular audits by human experts. Errors may still occur, as with any automated system. Always consult the linked primary sources. Read our AI Editorial Policy.