Lymphocyte Immune Globulin, Anti-Thymocyte Globulin (Equine) | CMS Coverage Update

Summary: The Centers for Medicare & Medicaid Services modified its coverage policy for Lymphocyte Immune Globulin, Anti-Thymocyte Globulin (Equine), effective May 15, 2026. Here's what billing teams need to do.

This update touches a narrow but high-stakes drug category. Anti-thymocyte globulin (equine)—commonly known by the brand name Atgam—is used in aplastic anemia treatment and organ transplant rejection prevention. The Centers for Medicare & Medicaid Services has modified its coverage policy for this agent, and the effective date of May 15, 2026 gives billing teams a short runway to confirm their documentation and prior authorization workflows are aligned. This policy does not list specific CPT or HCPCS codes in the available data, so we'll walk through what billing teams need to know based on the drug's clinical profile and CMS billing guidelines.

Quick-Reference Table

CMS Anti-Thymocyte Globulin (Equine) Coverage Criteria and Medical Necessity Requirements 2026

Anti-thymocyte globulin (equine) sits in a complicated billing space. It's a biologic agent administered in inpatient and outpatient hospital settings, and CMS coverage has always been tied tightly to documented medical necessity. This modification signals that CMS is tightening or clarifying something in that chain—whether that's indication criteria, documentation requirements, or administration settings.

The CMS anti-thymocyte globulin coverage policy applies to Medicare beneficiaries receiving this agent for approved indications. The two primary clinical uses are treatment of aplastic anemia—particularly severe aplastic anemia (SAA) in patients who are not candidates for bone marrow transplant—and prevention or treatment of acute renal allograft rejection in transplant patients. Each use carries its own medical necessity burden, and your documentation needs to reflect the specific indication explicitly.

For aplastic anemia, medical necessity documentation should establish the severity of the diagnosis, why bone marrow transplant is not the preferred or available treatment, and prior treatment history. For transplant rejection indications, the documentation should connect the drug administration to a specific rejection episode or to prophylactic protocols tied to the transplant event. Generic "immunosuppressive therapy" language on a claim is a fast path to a claim denial.

Prior authorization is a real concern here. Medicare Advantage plans—which follow CMS coverage policy as a baseline but add their own prior auth layers—frequently require PA for anti-thymocyte globulin. Even in traditional fee-for-service Medicare, where prior authorization is less common for Part B drugs, this modification may signal new utilization management requirements. Check with your Medicare Administrative Contractor (MAC) before May 15, 2026 to confirm whether your jurisdiction has a local coverage determination (LCD) that now intersects with this modified policy.

CMS Anti-Thymocyte Globulin (Equine) Exclusions and Non-Covered Indications

The available policy data does not provide a specific exclusions list. That said, based on the drug's known clinical profile and standard CMS billing guidelines, there are uses that consistently fall outside covered territory.

Off-label use without strong clinical evidence is the biggest exposure point. CMS does not broadly cover off-label biologics unless there's compendia support—specifically from sources like the American Hospital Formulary Service (AHFS), DRUGDEX, or recognized clinical guidelines. If your team is billing anti-thymocyte globulin (equine) for an indication that isn't aplastic anemia or transplant rejection, you need documented compendia support in the chart before the claim goes out.

Duplicate immunosuppressive therapy is another risk. Billing anti-thymocyte globulin (equine) alongside other T-cell depleting agents in the same treatment course requires clear clinical justification. CMS systems flag concurrent immunosuppressive regimens, and without documented rationale, reimbursement is at risk.

Coverage Indications at a Glance

Note: This policy does not list specific CPT or HCPCS codes in the available data. See the Affected Codes section below.

CMS Anti-Thymocyte Globulin Billing Guidelines and Action Items 2026

This is where most billing teams drop the ball—not because they don't know the policy, but because they don't translate it into workflow changes before the effective date. Do that now.

CPT, HCPCS, and ICD-10 Codes for Anti-Thymocyte Globulin (Equine) Under This CMS Policy

A Note on Code Data

This policy does not list specific CPT, HCPCS, or ICD-10 codes in the available policy data. PayerPolicy publishes the exact codes when they appear in the source document. In this case, they do not.

Anti-thymocyte globulin (equine) billing typically involves J-codes for injectable biologics, billed in the outpatient hospital or infusion center setting under Medicare Part B. The specific HCPCS code for Atgam (lymphocyte immune globulin, anti-thymocyte globulin equine) and the corresponding ICD-10-CM codes for aplastic anemia and transplant rejection are the codes your billing team needs to verify directly with your MAC or through your drug billing reference.

Do not assume the code hasn't changed just because this policy doesn't list one. Part of your pre-May 15, 2026 workflow should include confirming the correct HCPCS code with your MAC and verifying that code maps correctly to this modified coverage policy in your billing system.

Verify These Code Categories With Your MAC

If you're billing anti-thymocyte globulin (equine) billing in a hospital outpatient department, confirm that your revenue code and HCPCS code combination is consistent with the modified coverage policy requirements. Mismatches here are a common source of claim denial that doesn't get flagged until a MAC audit.