Per-milligram charge for an injection of narsoplimab-wuug, billed by each milligram given

Narsoplimab-wuug (Omeros' OMIDUBICEL-adjacent MASP-2 inhibitor, marketed as Narsoplimab) is a monoclonal antibody targeting mannan-binding lectin-associated serine protease-2 (MASP-2), a key effector of the lectin pathway of complement activation. This code captures per-milligram billing for intravenous administration of this agent, used in the treatment of hematopoietic stem cell transplant-associated thrombotic microangiopathy (HSCT-TMA). Dosing is weight-based, so units billed will reflect the total milligrams administered per encounter.

This code applies when narsoplimab-wuug is administered to patients with HSCT-TMA, a life-threatening complication characterized by endothelial injury, microangiopathic hemolytic anemia, thrombocytopenia, and organ dysfunction following stem cell transplantation. Documentation supporting use should include the confirmed HSCT-TMA diagnosis, the calculated dose in milligrams, and the administration record. Bill the number of units equal to the total milligrams administered (e.g., 370 mg = 370 units).

• Unit calculation is critical: This is a per-1 mg code; failure to multiply units to match total mg administered is a common underbilling error — verify the dose in the infusion/pharmacy record before submitting.
• Pair with the appropriate administration code: Report the IV infusion administration separately (e.g., relevant CPT infusion codes); narsoplimab is typically given as an IV infusion, so initial vs. sequential infusion rules apply.
• Payer coverage is limited and often requires prior authorization: As an FDA-designated drug with Breakthrough Therapy designation, coverage policies vary significantly; confirm medical necessity documentation aligns with payer-specific criteria and ensure the HSCT-TMA diagnosis code is clearly supported in the record.