Capillary zone electrophoresis (CZE), size exclusion chromatography (SEC), reducing sodium dodecyl sulfate capillary electrophoresis (rCE-SDS), and non-reducing sodium dodecyl sulfate capillary electrophoresis (nrCE-SDS) were performed according to the qualified methods as described in publications 2 and 3 of this series [11, 12]. To establish homogeneity and assign reference values, one 150 μL vial fraction (prepared as described in the ESM) was analyzed from three racks (racks 1, 50, 90) of each lot of RM 8671 (n = 3 vials per lot). The standard protocol for each lot was to perform triplicate repeatability on one vial and individual measurements on two additional vials for physicochemical value assignment. In some cases, deviations from this sampling sequence were required to allow analysis of all three lots within 24 h as described in ESM. Thaw/Freeze stability samples were analyzed from lot 14HB-D-001 vials that had undergone 1 or 5 thaw/freeze cycles at either −80 °C or −20 °C, for a total of 4 samples. Accelerated stability samples were analyzed from lot 14HB-D-001 vials that had undergone incubation at 4 °C, room temperature, or 40 °C for zero, 7, or 28 days for a total of 7 samples; an additional time point of 1 day at each temperature was analyzed by SEC. Method performance was evaluated on the day of analysis by injections of the method-specific instrument quality control standard (IQ) and PS 8670 as the system suitability standard that bracketed injections of RM 8671. The generic injection sequence was: Blank - IQ - PS 8670 - test samples (no more than 10) - IQ - PS 8670 – Blank, and was repeated as necessary to analyze all samples. Instrument qualification and system suitability controls were required to pass method performance criteria as outlined during method qualification [11, 12]. Data analysis for each method was performed as described in the requisite qualification paper [9, 11, 12]. Combined standard uncertainty (uc) for RM 8671 samples were calculated as described in ESM. The combined standard uncertainty is intended to represent, at the level of one standard deviation, the effect of the combined components of uncertainty including Type A measurement uncertainty and Type B components related to intermediate precision as observed during method qualification.