EXCERPT:
Most labs run ELISA for residual host cell protein — but ELISA only tells you how much is there, not what it is. That distinction matters more than most teams realize before filing.
CONTENT:
Most bioanalytical labs default to ELISA for residual host cell protein (HCP) testing, and for routine lot release that’s often sufficient. But there’s a critical gap: ELISA gives you a quantity, not an identity.
Twenty parts per million of HCP sounds manageable. But 20 ppm of a lipase is a different story entirely. Lipases degrade polysorbate stabilizers — the same surfactants that keep your drug product stable on the shelf. By the time degradation is visible, you may already have a comparability problem or a patient safety issue.
LC-MS fills that gap. Mass spectrometry identifies the specific proteins present, allowing risk-based decisions about which HCPs matter and which don’t. As regulators increasingly expect sponsors to understand their HCP profiles — not just quantify them — the combination of ELISA for quantity and LC-MS for identity is becoming the standard expectation, not a premium add-on.
For CROs supporting late-phase biologics and biosimilar programs, offering both methods isn’t just a capability differentiator. It’s a regulatory readiness conversation worth having early.