**3. Materials and Methods**

#### *3.1. Drug Product NMR Samples*

All the drug products (DP) listed in Table 1 were sourced from the US market except Reditux®, which was sourced from the India market. The DPs used for similarity metrics calculations were 7 lots of Rituxan®, 3 lots of Reditux®, 5 lots of Lantus® and 5 lots of Basaglar® (Table S1). NMR samples were prepared by directly mixing 0.5 mL of DP formulation with 0.03 mL of deuterium oxide, which contained 0.002% of trimethylsilylpropanoic acid (TMSP) or trimethylsilylpropanesulfonate sodium (DSS), then transferring to a 5 mm NMR precision tube (Wilmad-LabGlass).

#### *3.2. NMR Spectrsocopy*

All the NMR spectra were collected at experimental temperature of 25 ◦C. The NMR spectrometers were either a Bruker (Billerica, MA, USA) 850 MHz equipped with a cryogenic QCI probe or a Bruker 600 MHz equipped with a liquid nitrogen-cooled prodigy TCI probe.
