WHO/BS/2019.2366 WHO 1st IS for Insulin, human

Overview

Stocks of the 1st IRP, 66/304, are exhausted, and there is currently no provision of a reference material for the standardisation of human insulin immunoassays. A candidate preparation of pure human insulin was prepared in ampoules coded 11/212. A collaborative study was organised with 19 laboratories in 11 countries in two phases. In Phase 1, the candidate preparation was value assigned in SI units using a mass balance approach, with confirmatory data provided by HPLC and total nitrogen analysis. Phase 2 was designed to provide confirmatory data on the immunoreactivity of the candidate standard and its suitability to serve as an International Standard for the calibration of immunoassays of human insulin. This phase was also designed to assess the commutability of the candidate preparation, 11/212, in insulin immunoassays.

Participants were sent sub-portions of the active pharmaceutical ingredient (API) used to prepare the candidate standard, 11/212, and were requested to perform the mass balance tests using these sub-portions. The data obtained was combined with the 11/212 fill data in order to assign an insulin content to 11/212. Upon initial data analysis from Phase 1 of the study, it became apparent that smaller weights of active pharmaceutical ingredient (API) had been subject to a drying effect during sub-portioning, resulting in lower estimates of the insulin content of the candidate standard by HPLC assay compared with the expected content determined by mass balance. Participants were sent additional sub-portioned bulk API in a repeat of Phase 1. Data from the Phase 1 repeat mass balance assessment of the bulk API was used in conjunction with 11/212 fill data to assign a final insulin content to the candidate 11/212 of 9.19 mg/ampoule, with expanded uncertainty of 9.14 – 9.24 mg/ampoule (k=2). This value assignment was in good agreement with the estimated content of insulin observed using orthogonal methods of total nitrogen analysis (9.14 mg/ampoule (expanded uncertainty 8.97 – 9.30 mg/ampoule (k=2)) and by HPLC assay (9.19 mg/ampoule (expanded uncertainty 9.07 – 9.31mg/ampoule (k=2)).