Gamifant (emapalumab-lzsg) — HCPCS J9210

Gamifant in HLH therapy context — what it is, where it fits FDA verified May 2026

First-in-class anti-interferon-gamma mAb. There is no biosimilar and no direct competitor with the same mechanism. Sequencing relative to HLH-94 / HLH-2004 protocols is the coding question.

Gamifant (emapalumab-lzsg, J9210) is the only FDA-approved targeted therapy for primary HLH. It is a fully human IgG1 monoclonal antibody that binds and neutralizes interferon-gamma (IFN-γ), the dominant cytokine driving the HLH hyperinflammatory cascade. The biology is mechanistic: in primary HLH, defective cytotoxic function (perforin / granule-release pathway) leads to persistent T-cell and macrophage activation, sustained IFN-γ release, and a self-amplifying cytokine storm with multi-organ injury. Neutralizing IFN-γ interrupts the loop. There is no biosimilar; no other anti-IFN-γ product is approved.

Coding context matters because Gamifant is positioned after standard HLH chemotherapy, not in place of it. The HLH-94 protocol (etoposide + dexamethasone + cyclosporine A, with intrathecal therapy for CNS involvement) and its successor HLH-2004 are the international Histiocyte Society regimens for front-line induction. Emapalumab is approved for patients in whom that backbone has failed (refractory), relapsed after initial response (recurrent), continues to progress on therapy (progressive), or who cannot tolerate it (intolerant). Many transplant centers use Gamifant specifically as a bridge to allogeneic HSCT — controlling HLH activity through the donor search, conditioning, and engraftment window.

Dosing & unit math FDA label current

Weight-based, escalating to clinical response. Per the 2018 Gamifant USPI (BLA 761107) and the 2020 NEJM pivotal trial publication (Locatelli et al., NI-0501-04).

Dose schedule per FDA label

• 1 unit = 1 mg under J9210
• Infusion time: ~1 hour through a 0.2-micron in-line filter (per label); diluted in 0.9% NaCl
• Pediatric: newborn (>=0 days) and older — no minimum age or weight
• Adult: labeled (primary HLH is rare in adults but real, often unmasked by infection / malignancy trigger)
• No fixed treatment duration: treatment continues to allogeneic HSCT or as long as needed to control HLH activity
• Concomitant therapy: Gamifant is given with dexamethasone per the FDA label and the NI-0501-04 trial protocol (background dexamethasone is continued, with escalation or reduction per response)

Dosing — HLH / MAS in Still's disease (2025 sBLA indication)

The Still's-MAS regimen is materially different from primary HLH dosing: it uses a higher fixed Day 1 loading dose and a defined transition schedule rather than a 1 mg/kg starting dose with stepwise titration.

Per-dose unit math by weight

Worked example — 15 kg infant at 1 mg/kg starting dose

Required pre-administration checks

• Baseline TB evaluation — IGRA preferred over TST in immunosuppressed populations; chest imaging if positive (Warnings & Precautions, FDA label)
• Treat latent TB before initiating Gamifant (per label)
• Establish infection prophylaxis regimen: herpes zoster, Pneumocystis jirovecii, fungal (per label)
• Baseline and serial monitoring for CMV, EBV, adenovirus reactivation
• Document HLH-2004 criteria (5 of 8) or HScore for the diagnosis anchor
• Document HLH-94 / HLH-2004 conventional therapy course (regimen, dates, response, reason for switch)
• Document HSCT donor search status if bridge-to-HSCT intent
• Confirm dexamethasone background per protocol

NDC reference FDA NDC Directory verified May 2026

Administration codes CPT verified May 2026

Gamifant is a non-chemotherapeutic monoclonal antibody given as a ~1-hour IV infusion every 3 days.

Modifiers CMS verified May 2026

JZ — no drug discarded

Effective July 1, 2023, CMS requires JZ on all claims for single-dose container drugs when no drug is discarded. Because Gamifant has three vial sizes (10, 50, 100 mg), pharmacy can frequently combine vials to produce zero-waste doses. Example: 70 mg dose (70 kg adult at 1 mg/kg) = 1×50 + 2×10 = 70 mg drawn, no waste — bill 70 units J9210 with JZ. JZ is the expected modifier when vials combine exactly to the dose.

JW — drug discarded from a single-dose vial

When the patient's weight-based dose does not combine exactly to vial multiples, document the discarded mg and bill it on a separate line with JW. Gamifant SDVs cannot be reused across patients. Use the least-waste vial combination per CMS guidance.

Worked JW example — 15 mg dose (15 kg infant at 1 mg/kg)

Modifier 25 — situational

Use modifier 25 on the E/M code when a significant, separately identifiable evaluation and management service is performed on the same day as administration. Routine pre-administration weight check, vitals, and infusion-readiness assessment are bundled into the admin code.

340B modifiers (JG, TB)

Pediatric oncology / transplant centers that are 340B-eligible should follow their MAC's current 340B modifier policy on J9210. Emapalumab's high ASP makes 340B economics meaningful at high-volume transplant centers; verify site-specific contract terms before electing.

ICD-10-CM diagnosis codes FY2026 verified May 2026

D76.1 is the primary anchor for HLH; Still's-associated MAS adds the Still's / sJIA codes.

Site of care & place of service Verified May 2026

Primary HLH is an acute, often critically ill presentation — the typical induction phase happens inpatient in a PICU or NICU at a tertiary pediatric or adult transplant center. As the patient stabilizes and approaches HSCT, the regimen often continues in the hospital outpatient department (HOPD) or in the hematology / transplant clinic office as an outpatient bridge. Home administration is not appropriate for the J9210 population — these are acute, fragile, immunosuppressed patients with frequent monitoring needs.

Claim form field mapping Verified May 2026

CMS-1500 / 837P for outpatient bridge phase (POS 11 / 19 / 22 / 49). UB-04 / 837I for inpatient (POS 21) is charge-master only — bundled into DRG.

Form references: NUCC (CMS-1500).

Payer policy snapshot Reviewed May 2026

PA universal; HLH-94 / HLH-2004 conventional-therapy step is the dominant requirement; reauthorization every 4 to 8 weeks tied to HSCT planning.

What to document for approval

• Confirmed HLH diagnosis (HLH-2004 criteria met, HScore value, or molecular diagnosis)
• Active disease markers: ferritin (often markedly elevated), sCD25, NK-cell activity, cytopenia profile, fibrinogen, triglycerides
• HLH-94 or HLH-2004 conventional-therapy course documented (regimen, dates, outcome — refractory / recurrent / progressive / intolerant)
• Baseline TB screening result (IGRA preferred; chest imaging if positive); latent TB treated if applicable
• Infection prophylaxis regimen (herpes zoster, P. jirovecii, fungal per label)
• CMV / EBV / adenovirus baseline and monitoring plan
• HSCT donor search status and planned transplant timeline (for primary HLH bridge intent)
• For Still's-MAS (2025 sBLA expansion): AOSD / sJIA diagnosis history, MAS-specific criteria
• Background dexamethasone regimen per protocol

Medicare reimbursement CMS Q2 2026 (live)

Quarterly ASP from CMS Part B Drug Pricing File. Refreshes automatically each quarter. Inpatient courses bundle into the DRG; only outpatient Part B billing is separately payable under J9210.

Per-dose reimbursement — Q2 2026

Coverage

No NCD specific to emapalumab. Coverage falls under the generic drug-coverage LCD framework, with commercial and Medicare Advantage payers applying their HLH-specific medical policies. All MACs cover J9210 for FDA-approved on-label use (primary HLH refractory / recurrent / progressive / intolerant; and the 2025 sBLA expansion for HLH / MAS in Still's disease) when the standard PA criteria are met. Inpatient induction is bundled into the DRG payment; only outpatient Part B billing is separately payable.

Code history

• November 20, 2018 — FDA approval (BLA 761107); initially billed under unclassified codes (J3590 / C9399) for early-launch DOS
• January 1, 2019 — C9462 (transitional pass-through) assigned
• April 1, 2019 — permanent HCPCS code J9210 assigned, "Injection, emapalumab-lzsg, 1 mg" (1 mg = 1 unit)
• Q2 2026 — ASP+6% payment limit $384.135 per mg
• 2025 — sBLA approved for HLH / MAS in Still's disease (label expansion)
• Next ASP update: July 1, 2026 for Q3

Patient assistance — Gamifant Cares (Sobi) Sobi verified May 2026

Sobi operates the Gamifant Cares hub for benefits verification, prior authorization support, co-pay assistance, and patient assistance.

• Gamifant Cares (Sobi patient support): 1-833-597-6530 (M–F, business hours)
• Web: gamifantcares.com
• Sobi Medical Information: 1-866-773-5274 · medinfo.us@sobi.com
• Gamifant Co-pay Program: commercial copay assistance for eligible commercially insured patients. Excludes Medicare, Medicaid, TRICARE, VA, and other federal-program patients per federal anti-kickback rules.
• Sobi Patient Assistance Program (PAP): free drug for eligible uninsured / underinsured patients via Gamifant Cares; income / clinical-need criteria apply
• Independent foundation referral: Gamifant Cares routes Medicare and Medicaid patients to independent co-pay foundations (PAN, HealthWell, NORD, Good Days) as funding allows

Independent foundations (for Medicare / Medicaid / uninsured)

• NORD (National Organization for Rare Disorders) — primary HLH and rare-disease funds open intermittently
• PAN Foundation — rare-disease funds applicable to HLH open as funding allows
• HealthWell Foundation — periodic rare-disease funds
• Good Days — occasional rare / pediatric disease funds
• Histiocytosis Association (histio.org) — HLH-specific patient resources and family support; not a co-pay fund but a connection point for the broader histiocytosis community

Common denials & how to fix them

Frequently asked questions

What is the HCPCS code for Gamifant (emapalumab)?

Gamifant (emapalumab-lzsg) is billed under HCPCS J9210 — "Injection, emapalumab-lzsg, 1 mg." Each 1 mg equals one billable unit, so a 15 mg dose (15 kg infant at 1 mg/kg) is 15 units, a 70 mg dose (70 kg adult at 1 mg/kg) is 70 units, and an escalated 6 mg/kg dose in a 30 kg child (180 mg) is 180 units. The product ships in three preservative-free single-dose vial sizes (all 5 mg/mL): 10 mg / 2 mL (NDC 66658-501-01), 50 mg / 10 mL (NDC 66658-505-01), and 100 mg / 20 mL (NDC 66658-510-01).

How are HLH diagnostic criteria (HLH-2004) documented for a J9210 prior authorization?

Payer policies for emapalumab uniformly require documentation of the HLH-2004 diagnostic criteria (or HScore for adults / secondary HLH). The HLH-2004 criteria require either (a) a molecular diagnosis consistent with HLH (e.g., PRF1, UNC13D, STX11, STXBP2, RAB27A, SH2D1A, XIAP variants), OR (b) at least 5 of the following 8: fever; splenomegaly; cytopenias (≥2 lineages); hypertriglyceridemia and/or hypofibrinogenemia; hemophagocytosis in bone marrow / spleen / lymph nodes; low or absent NK-cell activity; ferritin ≥500 mcg/L; elevated soluble CD25 (sIL-2R). Most payers also require documentation of inadequate response to, refractory disease on, recurrence after, or documented intolerance of conventional HLH therapy (typically dexamethasone + etoposide per HLH-94 or HLH-2004 protocols).

Is prior failure of HLH-94 / HLH-2004 conventional therapy required?

Per the FDA label, Gamifant is indicated for primary HLH patients with refractory, recurrent, or progressive disease, OR intolerance to conventional HLH therapy. Conventional HLH therapy means the HLH-94 or HLH-2004 backbone (dexamethasone + etoposide, with intrathecal therapy for CNS involvement and cyclosporine A in HLH-94). The PA package should include: regimen used (HLH-94 vs HLH-2004), induction start and end dates, response criteria assessed (fever resolution, ferritin trend, sCD25 trend, cytopenia recovery), and the specific reason for switching (refractory = no response, recurrent = relapse after initial response, progressive = worsening on therapy, intolerant = unacceptable toxicity). Front-line emapalumab without documented conventional therapy is generally not covered unless contraindication to etoposide is documented.

How is pediatric ICU administration of Gamifant billed?

Critically ill HLH patients are commonly inpatient (PICU / NICU) during induction. In the inpatient setting, J9210 is bundled into the DRG payment — it is NOT separately payable on Part A claims. Document drug administration in the chart and on the UB-04 (revenue code 0636 with HCPCS for charge-master tracking) but do not expect separate reimbursement. Only when the patient stabilizes enough to transition to hospital outpatient department (HOPD POS 19/22), ambulatory infusion center (POS 49), or hematology / transplant clinic office (POS 11) does J9210 become separately payable under Part B. Most pediatric primary-HLH courses span inpatient induction plus outpatient bridge-to-HSCT — bill J9210 only on the Part B side.

How does dose escalation from 1 mg/kg up to 10 mg/kg affect billing?

Per the FDA label, the starting dose is 1 mg/kg IV every 3 days; this can be increased to 3 mg/kg, 6 mg/kg, and up to 10 mg/kg based on clinical and laboratory response (e.g., fever, ferritin, sCD25, cytopenias, fibrinogen, liver function). Each escalation step is documented in the chart and the new dose is billed at the new mg/kg multiplier — there is no per-dose ceiling under J9210. For a 30 kg child, that progression looks like 30 units (1 mg/kg) → 90 units (3 mg/kg) → 180 units (6 mg/kg) → 300 units (10 mg/kg) per dose. Re-authorization at escalation steps is common with commercial payers; document the trigger labs and the clinical rationale for each increase.

What is the expected bridge-to-HSCT timeline for Gamifant?

Per the FDA label and the NI-0501-04 pivotal trial (NEJM 2020), Gamifant is intended as a bridge to allogeneic hematopoietic stem cell transplantation (HSCT) for primary HLH — treatment continues until allogeneic HSCT or as long as needed to control HLH activity. In the pivotal trial, the median duration of emapalumab therapy was approximately 60 days (with substantial range). Payer reauthorizations are typically 4 to 8 weeks, with HSCT planning documentation expected at each renewal. Discontinuation should follow HSCT conditioning or, in rare cases, sustained remission off therapy. Document the HSCT donor search status, conditioning regimen plan, and transplant center coordination at every reauthorization window.

Is TB screening required before Gamifant?

Yes. Per the FDA label's Warnings & Precautions section on serious infections (Gamifant carries no boxed warning), evaluate patients for tuberculosis (TB) risk factors and test for latent infection before initiating Gamifant. Patients with latent TB should receive standard treatment before starting emapalumab. Serious infection risk also covers opportunistic infections, including viral (CMV, HSV, EBV reactivation), fungal (histoplasmosis, Pneumocystis jirovecii), and bacterial pathogens. Prophylaxis against herpes zoster, P. jirovecii pneumonia, and fungal infection should be administered per the label. The chart should document: TB screening result (IGRA preferred over TST in immunosuppressed; chest imaging if positive); CMV / EBV / adenovirus monitoring plan; and the prescribed infection-prophylaxis regimen. Missing TB screening is a frequent payer-PA denial.

Is Gamifant approved for adult HLH coverage?

Yes. Gamifant's FDA-approved indication explicitly includes adult and pediatric (newborn and older) patients with primary HLH that is refractory, recurrent, or progressive, or who are intolerant to conventional HLH therapy. The historical perception that HLH is a pediatric disease comes from the genetic / familial HLH subset that presents in infancy; primary HLH in adults is rarer but real (often unmasked by triggering infection or malignancy), and emapalumab is labeled for both populations. Adult coverage policies often require additional documentation of underlying genetic / familial HLH workup or careful exclusion of secondary causes (malignancy-associated HLH, infection-associated HLH, MAS in Still's disease — the last now also FDA-approved for Gamifant per the 2025 sBLA expansion). Use D76.1 (HLH) as the primary diagnosis.

Source documents

1. FDA — Gamifant (emapalumab-lzsg) Prescribing Information, 2018
   Original FDA-approved label (BLA 761107), with the W&P serious-infection section, dose escalation schedule, and primary HLH indication. (Note: original and current Gamifant labels do not contain a boxed warning.)
2. DailyMed — GAMIFANT (emapalumab-lzsg) Prescribing Information
   SetID a865e0ef-8685-4f69-8838-648c4f3bab47 (Sobi); most recent revision March 26, 2026 (current Still's-disease MAS indication, no boxed warning)
3. FDA — Gamifant Approval Letter, November 20, 2018
   BLA 761107 approval letter; primary HLH indication for pediatric (newborn and older) and adult patients
4. Locatelli F, et al. — Emapalumab in Children with Primary Hemophagocytic Lymphohistiocytosis (NI-0501-04). NEJM 2020;382:1811-1822
   Pivotal phase 2/3 trial supporting FDA approval (NEJM 2020)
5. Gamifant Cares — Sobi patient support
   Benefits verification, prior authorization support, Copay Program, PAP · 1-833-597-6530
6. Sobi North America — Patient support
   Sobi US patient support and medical information access (medinfo.us@sobi.com / 1-866-773-5274)
7. Henter J-I, et al. — HLH-2004: Diagnostic and Therapeutic Guidelines for Hemophagocytic Lymphohistiocytosis. Pediatr Blood Cancer 2007;48:124-131
   Histiocyte Society HLH-2004 diagnostic criteria + treatment protocol (5-of-8 criteria framework)
8. Fardet L, et al. — Development and validation of the HScore, a score for the diagnosis of reactive hemophagocytic syndrome. Arthritis Rheumatol 2014;66:2613-2620
   HScore (probabilistic adult HLH diagnostic tool), often accepted alongside HLH-2004
9. NORD — Hemophagocytic Lymphohistiocytosis (HLH)
   Patient-facing HLH overview; foundation funding contacts
10. Histiocytosis Association
    HLH-specific patient community resources and family support
11. CMS — Medicare Part B Drug ASP Pricing File
    Q2 2026 quarterly file, effective April 1 – June 30, 2026
12. CMS — HCPCS quarterly update file (canonical J-code source)
    J9210 permanent code effective April 1, 2019 (replaced C9462 transitional pass-through)
13. FDA National Drug Code Directory
    NDCs 66658-501-01, 66658-505-01, 66658-510-01 (Sobi labeler 66658)

About this page

We maintain this page as a living reference. Medicare ASP pricing is bound to our underlying CareCost data layer and refreshes automatically when CMS publishes new quarterly files. Coding and policy content is reviewed at least quarterly and updated whenever a source document changes.

Found an error? Email hello@carecostestimate.com.

Refresh cadence

Reviewer

Change log

• May 23, 2026 — SME audit pass. Removed mischaracterization of W&P serious-infection language as a "boxed warning" (current label has no boxed warning). Added Still's-disease MAS dosing schedule from the 2025 sBLA. Refreshed DailyMed link to setid a865e0ef-8685-4f69-8838-648c4f3bab47 (rev Mar 26, 2026). Pricing and primary HLH dosing unchanged.
• May 22, 2026 — Initial publication. ASP data: Q2 2026 (J9210 = $384.135 per mg). FDA approval verified November 20, 2018 (BLA 761107) for primary HLH; 2025 sBLA expansion for HLH / MAS in Still's disease noted. NDCs verified 66658-501-01 (10 mg / 2 mL), 66658-505-01 (50 mg / 10 mL), 66658-510-01 (100 mg / 20 mL), all 5 mg/mL preservative-free single-dose vials. Dose schedule verified against the 2018 FDA label and the 2020 NEJM pivotal trial publication (NI-0501-04, Locatelli et al.): 1 mg/kg IV q3d starting dose, escalating stepwise to 3, 6, and up to 10 mg/kg per clinical / laboratory response, continued until allogeneic HSCT or as needed to control HLH activity. Gamifant Cares contact verified 1-833-597-6530. Sobi Medical Information: 1-866-773-5274.

Methodology

Every claim on this page is sourced inline. Pricing reflects the current CMS Part B Drug ASP Pricing File. Payer policies are read directly from each payer's published medical / pharmacy policy documents. We do not paraphrase from billing-software vendor blogs. The dose escalation schedule and infusion guidance are taken from the 2018 Gamifant USPI (BLA 761107) and cross-checked against the NI-0501-04 pivotal trial publication (NEJM 2020). The HLH-2004 diagnostic criteria framework is taken from the Histiocyte Society protocol (Henter et al., 2007). Vial-waste calculations are derived from the FDA-labeled weight-based doses combined with the three 5 mg/mL single-dose vial sizes. When payer guidance is inconsistent (as with off-label use in secondary HLH outside the Still's-MAS approval), we surface the ambiguity rather than asserting a definitive answer.