HCPCS code J2329: Billing guide for ublituximab-xiiy (Briumvi)

Key Takeaways

HCPCS code J2329 describes Injection, ublituximab-xiiy, 1 mg (Briumvi), a monoclonal antibody for relapsing forms of multiple sclerosis, effective July 1, 2023.

Billing unit is 1 mg per unit; a standard 450 mg infusion requires 450 units on the claim. CMS classifies J2329 as a single-dose container.

JW and JZ wastage modifiers are mandatory for J2329 under CMS policy. Always report the administered quantity on one line and any wasted drug on a separate line with modifier JW.

UnitedHealthcare Exchange plans require prior authorization for J2329. Check each payer individually as coverage policies vary and are updated frequently.

Pabau’s claims management software helps infusion practices track drug units, apply modifiers correctly, and submit clean J2329 claims the first time.

The official long descriptor for HCPCS code J2329 is: Injection, ublituximab-xiiy, 1 mg. The short descriptor is: Inj ublituximab-xiiy, 1 mg. CMS placed J2329 under the HCPCS Level II category “Drugs Administered Other than Oral Method,” consistent with other infused biologics in the J-code range.

Ublituximab-xiiy (brand name Briumvi, manufactured by TG Therapeutics) received FDA approval for adult patients with relapsing forms of multiple sclerosis. Relapsing forms include relapsing-remitting MS (RRMS), active secondary progressive MS, and clinically isolated syndrome meeting diagnostic criteria.

The drug is administered as an intravenous infusion, making it a Part B covered drug in an outpatient or infusion-center setting.

CMS established the permanent J-code via the HCPCS Q3 2023 update cycle, assigning J2329 effective July 1, 2023. Before that date, Briumvi was billed under the miscellaneous code J3590 (unclassified biologics), so practices should audit any J3590 Briumvi claims from January through June 2023 for proper documentation.

Dosage, billing units, and the single-dose container rule

The billing unit for J2329 is 1 mg per unit. Each unit reported on the claim represents 1 mg of ublituximab-xiiy administered or wasted. This is the most common source of unit errors: coders who report the number of vials rather than the number of milligrams.

The standard Briumvi dosing regimen consists of an initial dose of 150 mg on Day 1 followed by 450 mg on Day 15. Subsequent doses are 450 mg every 24 weeks. For a 450 mg infusion, the claim should report 450 units of J2329 (450 x 1 mg = 450 units). For the initial 150 mg dose, report 150 units.

CMS has designated J2329 as a single-dose container code. This classification is significant because it triggers mandatory JW/JZ modifier requirements, covered in the next section. Single-dose vials cannot be pooled or combined for multiple patients, and any drug remaining in the vial after administration is considered waste subject to modifier reporting rules under CMS policy.

Quick reference: Billing units by dose

Software with built-in drug-unit calculators reduces J2329 unit errors: when the drug’s dose parameters are pre-configured, billing staff get accurate milligram counts without manual math. For teams new to drug-code billing, the medical billing primer covers how HCPCS units flow onto a claim.

JW and JZ modifier requirements

CMS’s JW/JZ modifier policy applies to all HCPCS codes identified as single-dose containers, and J2329 is on that list. Incorrect or missing modifiers are the primary reason J2329 claims are flagged during post-payment review.

Here is how the two modifiers work in practice:

• Modifier JZ – Report when the entire vial contents are administered and there is zero waste. Append JZ to the J2329 line and report the full administered quantity. This tells the payer no drug was discarded.
• Modifier JW – Report when drug remains in the vial after administration (waste occurs). Split the claim line: one line for the administered quantity (no modifier or with JZ if no waste on that specific vial), and a separate line for the wasted quantity with modifier JW appended. The sum of both lines equals the total drug drawn from the vial.

For Briumvi specifically: the drug is supplied as 150 mg/10 mL (15 mg/mL) vials, so a 450 mg dose requires three vials. If all three vials are fully used, report 450 units of J2329 with modifier JZ.

If any vial yields less than the full 150 mg due to preparation loss, report the administered quantity on one line and the wasted quantity with modifier JW on a separate line.

Document waste in the infusion record at time of service. CMS auditors expect contemporaneous documentation of waste amounts; retrospective reconstruction is not accepted.

Clean modifier documentation also supports claims management software that auto-validates modifier logic before submission, reducing denials before they reach the payer.

Prior authorization and payer coverage

Prior authorization (PA) requirements vary by payer and plan type and change without broad announcement. Practices that assume coverage based on a prior approval from a different plan or a prior year risk denials.

Confirmed payer requirements:

• UnitedHealthcare Exchange plans require prior authorization for J2329 (Briumvi), per UHC’s exchange plan prior authorization list effective April 1, 2025.
• Carelon Rx (formerly Anthem pharmacy management) added J2329 to its medical drug clinical criteria effective July 1, 2023, with step-therapy requirements. Briumvi may require evidence of prior MS disease-modifying therapy trials depending on the clinical policy version in effect.
• Medicare Part B: Coverage is available for medically necessary use in FDA-approved indications. No universal PA requirement under traditional Medicare, but Medicare Advantage plans set their own policies. Verify with the specific MA plan before infusion.

The safest practice: submit the PA request 14-21 days before the scheduled infusion date, and include the treating neurologist’s diagnosis documentation, most recent MRI findings (if available), and the specific ICD-10 diagnosis code.

Always cite the current version of the payer’s drug policy number when submitting. Carelon and UHC both publish clinical criteria documents that specify step-therapy requirements and evidence standards for Briumvi PA approvals.

Using digital intake forms that capture complete MS diagnosis history, prior treatment timelines, and relapse records at onboarding saves significant time when compiling PA submissions. Staff can pull the documented treatment history directly into the PA request rather than chasing paper records.

ICD-10 diagnosis codes for J2329

Every J2329 claim requires a supporting ICD-10-CM diagnosis code that documents medical necessity. The diagnosis code must reflect the FDA-approved indication: relapsing forms of multiple sclerosis in adult patients. Using a non-covered diagnosis or an MS code that does not match the patient’s clinical picture is a denial trigger and a potential audit flag.

Commonly used ICD-10-CM codes with J2329 (note: ICD-10-CM deleted the single code G35 effective October 1, 2025, under the FY2026 update and replaced it with the G35.A–G35.D subcategories below; for dates of service before October 1, 2025, G35 was reported):

Code specificity matters. Since the FY2026 update, plain G35 is no longer billable, and payers with active step-therapy requirements typically want the more specific relapsing-form subtype code to confirm eligibility.

The treating neurologist’s clinical notes must support the code selected. Avoid coding SPMS subtypes that are not active (e.g., G35.C2, non-active secondary progressive MS), since Briumvi’s indication requires the relapsing disease component.

Consult HIPAA compliance for medical offices when storing and transmitting patient diagnosis documentation electronically. For related infusion biologic billing, see the HCPCS Code S9379 home infusion therapy billing guide.

Simplify J2329 billing from order to reimbursement

Pabau helps infusion and neurology practices track drug units, apply JW/JZ modifiers, and submit clean claims. See how it handles complex biologic billing workflows.

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NDC crosswalk and claim submission

Some payers, including certain Medicare Advantage plans and commercial carriers, require an NDC (National Drug Code) to appear on the claim alongside J2329. When NDC reporting is required, it typically appears in Loop 2410 of the 837P electronic claim or in the appropriate UB-04 field for facility billing.

Briumvi NDC numbers are assigned by TG Therapeutics and appear on the product labeling and on invoices from the specialty pharmacy or distributor supplying the drug. The NDC format on claims is 11 digits (5-4-2 format).

When billing with an NDC, also report the unit of measure qualifier (“ME” for milligrams) and the NDC quantity, matching the total amount administered plus wasted.

The CMS HCPCS overview and AAPC’s HCPCS code lookup are the standard references for confirming current NDC crosswalk requirements and code-level billing guidance.

For fee schedule amounts, use the CMS Physician Fee Schedule lookup tool, which is updated quarterly and reflects current ASP-based payment rates for J-codes. Avoid citing dollar amounts from third-party aggregators without verifying against the current CMS ASP file, as rates change quarterly.

For buy-and-bill scenarios: the practice purchases Briumvi through a specialty distributor, administers it, and seeks reimbursement at ASP + a percentage add-on (the specific add-on rate for Medicare Part B is set by statute; commercial payers negotiate independently).

The standard Medicare Part B payment rate for separately payable drugs is ASP + 6% (subject to sequestration reduction, currently ASP + 4.3% after the 2% cut). Practices considering the buy-and-bill model for Briumvi should review their GPO contracts and storage requirements before committing.

Practices that prefer patient-specific acquisition use specialty pharmacy hub programs offered through TG Therapeutics.

J2329 compared to related MS drug codes

Coders working in neurology or infusion settings often encounter multiple anti-CD20 MS drugs in the same billing period. Understanding how J2329 relates to adjacent codes reduces crosscoding errors.

• J2350 – Injection, ocrelizumab, 1 mg: Ocrelizumab (Ocrevus, Roche/Genentech) is the other IV anti-CD20 MS biologic. J2350 uses the same per-milligram billing unit as J2329. A standard ocrelizumab 600 mg dose = 600 units of J2350. Do not swap J2329 and J2350 based on drug class; the codes are drug-specific.
• J2351 – Injection, ocrelizumab, 1 mg and hyaluronidase-ocsq: Covers the subcutaneous formulation of ocrelizumab (Ocrevus Zunovo). Subcutaneous administration does not apply to Briumvi; never substitute J2351 for J2329.
• J2327 – Injection, risankizumab-rzaa, intravenous, 1 mg: A different indication (plaque psoriasis, psoriatic arthritis, Crohn’s disease, ulcerative colitis). Risankizumab (Skyrizi) is not an MS drug. Listed here because it appears adjacent to J2329 in the HCPCS J2 code group range.
• J3590 – Unclassified biologics: The miscellaneous code used for Briumvi prior to July 1, 2023. J3590 claims require a letter of medical necessity and drug name as an attachment. Using J3590 instead of J2329 after the effective date is incorrect and will delay reimbursement.

Good EMR software for infusion practices maintains a drug master list mapped to current HCPCS codes, reducing the chance of a coder selecting J2350 when J2329 is the correct code for a Briumvi infusion encounter.

Step-by-step J2329 billing workflow

A clean J2329 claim starts before the day of infusion. Follow this workflow for neurology and infusion center billing teams:

1. Verify eligibility and plan type at least 5 business days before the infusion date. Confirm the patient’s active Part B or commercial coverage, MS diagnosis on file, and whether a PA is required for J2329 under the specific plan.
2. Obtain prior authorization if required. Include the ICD-10-CM diagnosis code (typically G35.A for relapsing-remitting MS), the treating neurologist’s clinical notes, prior MS therapy history, and the requested infusion date. Reference the payer’s current drug policy for Briumvi.
3. Confirm drug receipt and lot numbers before the infusion date. For buy-and-bill, verify drug storage conditions and note the NDC from the product labeling or pharmacy invoice.
4. Document the infusion in real time. Record pre-medication administration, infusion start and stop times, the dose administered (in mg), any adverse reactions, and the amount of drug remaining in each vial at completion.
5. Calculate units and modifiers after infusion. Total mg administered = units of J2329 with modifier JZ (if no waste) or split lines with JW for waste. Sum the administered and wasted quantities to reconcile against the vials opened.
6. Submit the claim with J2329, the correct unit count, the applicable JW/JZ modifier, the supporting ICD-10-CM code, and the NDC if required by the payer. Attach the infusion record if the payer requires it for high-cost biologics.
7. Follow up on remittance within 30 days. If denied, review the remittance advice for the denial reason code, check modifier documentation, and resubmit or appeal with supporting clinical notes.

Using prescription management software that links the drug order to the billing workflow ensures the administered dose, lot number, and modifier requirements are captured before the claim is submitted rather than reconstructed afterward. For practices building out their billing operations, practice management software with integrated claims submission reduces the manual handoffs where J2329 billing errors typically occur.

The infusion encounter is often billed alongside an evaluation and management visit such as CPT code 99213, and any pre-medication (for example, an antiemetic billed under HCPCS code J1626) is reported on its own line with the correct units.

Practices billing other high-cost injectable and infusion drugs may also find the per-milligram unit and modifier logic in these guides useful: HCPCS code Q5121 for infliximab-axxq (Avsola), HCPCS code J0894 for decitabine, HCPCS code J9145 for daratumumab, and HCPCS code J9041 for bortezomib.

Conclusion

Billing errors on high-cost biologics like Briumvi typically trace to unit miscounts, missing modifiers, and failed prior authorization — the same leak points a strong healthcare revenue cycle management process is built to catch.

J2329 requires clean documentation at every step: the correct per-milligram unit count, mandatory JW or JZ modifier reporting, a payer-specific PA, and the right ICD-10-CM relapsing-MS diagnosis code. Building these checks into the workflow before the infusion date prevents the denials that follow.

Pabau’s claims management software helps infusion centers and neurology practices track drug administration details, validate modifier logic, and submit complete J2329 claims from a single platform. See how it works by requesting a live demo.

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