Table 2.

The 25 most abundant downstream impurities assessed by emPAI in Protein A eluate of a therapeutic mAb. Proteins with specific immunoreactivity are noted in the anti-HCP coverage. Proteins described previously in the literature as downstream impurities in antibodies are noted. HCPs with specific immunoreactivity determined by unique identification in the anti-HCP immunocapture are denoted. HCPs with coverage determined by interrogation of differential protein abundance between the positive and negative affinity purifications are also noted using an ^αsuperscript. Among the top 25 impurities identified, only 2 lacked ELISA coverage as assessed by affinity purification.

Rank	Protein	Previously Described	Anti-HCP Coverage
1	Pyruvate kinase	Y	Yα
2	Glyceraldehyde-3-phosphate dehydrogenase		Y
3	Guanine nucleotide-binding protein subunit β-2-like 1	Y	Y
4	Macrophage metalloelastase (MMP-12)
5	40S ribosomal protein S3	Y	Yα
6	Nidogen-1	Y	Y
7	Serine protease HTRA1	Y	Yα
8	Complement C1q tumor necrosis factor-related protein 5	Y	Y
9	40S ribosomal protein S20		Yα
10	60S acidic ribosomal protein P0		Y
11	Fructose-bisphosphate aldolase	Y	Yα
12	Galectin-3-binding protein	Y	Y
13	60S ribosomal protein L12		Yα
14	Elongation factor 1-α	Y	Y
15	Clusterin	Y	Y
16	Actin, cytoplasmic 1	Y	Y
17	Phospholipid transfer protein		Y
18	Peptidyl-prolyl cis-trans isomerase		Yα
19	Lactadherin (Fragment)	Y	Yα
20	Retinoid-inducible serine carboxypeptidase		Yα
21	Lysosomal α-glucosidase	Y	Yα
22	GTP-binding nuclear protein Ran		Yα
23	Fibronectin		Yα
24	Elongation factor 2	Y	Yα
25	Heat shock protein HSP 90-α	Y