Pegfilgrastim (Neulasta, Amgen) is a pegylated granulocyte colony-stimulating factor (G-CSF) indicated to decrease the incidence of febrile neutropenia in patients with non-myeloid malignancies receiving myelosuppressive chemotherapy. Since Fulphila launched in 2018 as the first biosimilar, eight biosimilar pegfilgrastim products have reached the US market. As of Q2 2025, biosimilars held 87% of the pegfilgrastim market by volume.
Yet the pegfilgrastim market remains deeply unusual. Neulasta's own ASP has fallen below several biosimilars, creating a pricing inversion that distorts buy-and-bill incentives. Only one biosimilar on-body injector exists (Udenyca Onbody), leaving Neulasta Onpro as the dominant device option. Payer step-therapy hierarchies often prefer higher-ASP biosimilars over cheaper alternatives. And new products including Armlupeg and Rolvedon continue to enter.
This guide maps every approved pegfilgrastim product to its HCPCS code, explains ASP-based reimbursement mechanics, analyzes on-body injector gaps, and outlines what oncology clinics and access teams need to know for 2026 formulary positioning.
Short answer
| Neulasta (reference) | Biosimilars (collective) | |
|---|---|---|
| FDA-approved products | Neulasta prefilled syringe, Neulasta Onpro kit | Fulphila, Udenyca, Udenyca Onbody, Ziextenzo, Nyvepria, Stimufend, Fylnetra, Armlupeg |
| Non-pegfilgrastim G-CSF alternatives | Neupogen (filgrastim) | Rolvedon (eflapegrastim-xnst), Ryzneuta (efbemalenograstim alfa-vuxw) |
| HCPCS (reference) | J2506 — excludes biosimilar | — |
| HCPCS (biosimilars) | — | Q5108, Q5111, Q5120, Q5122, Q5127, Q5130, Q5169 |
| On-body injector | Neulasta Onpro (J2506) | Udenyca Onbody (Q5111) |
| Biosimilar market share (Q2 2025) | ~13% | ~87% |
| Average biosimilar ASP (Q4 2025) | $239.76/6 mg | $1,316/6 mg (average across biosimilars) |
| Medicare reimbursement | ASP + 6% | ASP + 8% of reference ASP (for qualifying biosimilars) |
| Interchangeability | Not applicable | None designated interchangeable as of May 2026 |
All FDA-approved pegfilgrastim products and HCPCS codes
Each biosimilar receives its own unique Q-code, separate from the reference product's J-code. This is a critical difference from small-molecule generic drugs, which share a single code with the reference. Separate coding means each biosimilar reports its own ASP, and providers are reimbursed based on that individual ASP, not a blended average.
| Brand | Nonproprietary name | Manufacturer | HCPCS code | Code descriptor | FDA approval | Available presentations |
|---|---|---|---|---|---|---|
| Neulasta | Pegfilgrastim | Amgen | J2506 | Injection, pegfilgrastim, excludes biosimilar, 0.5 mg | 2002 | Prefilled syringe 6 mg/0.6 mL, Onpro kit, vial 4 mg/0.4 mL |
| Fulphila | Pegfilgrastim-jmdb | Biocon/Viatris | Q5108 | Injection, pegfilgrastim-jmdb, biosimilar, (Fulphila), 0.5 mg | 2018 | Prefilled syringe 6 mg/0.6 mL |
| Udenyca | Pegfilgrastim-cbqv | Coherus/Intas | Q5111 | Injection, pegfilgrastim-cbqv, biosimilar, (Udenyca), 0.5 mg | 2019 | Prefilled syringe, autoinjector, Onbody |
| Ziextenzo | Pegfilgrastim-bmez | Sandoz | Q5120 | Injection, pegfilgrastim-bmez, biosimilar, (Ziextenzo), 0.5 mg | 2019 | Prefilled syringe 6 mg/0.6 mL |
| Nyvepria | Pegfilgrastim-apgf | Pfizer | Q5122 | Injection, pegfilgrastim-apgf, biosimilar, (Nyvepria), 0.5 mg | 2020 | Prefilled syringe 6 mg/0.6 mL |
| Stimufend | Pegfilgrastim-fpgk | Fresenius Kabi | Q5127 | Injection, pegfilgrastim-fpgk, biosimilar, (Stimufend), 0.5 mg | 2022 | Prefilled syringe 6 mg/0.6 mL |
| Fylnetra | Pegfilgrastim-pbbk | Amneal/Kashiv | Q5130 | Injection, pegfilgrastim-pbbk, biosimilar, (Fylnetra), 0.5 mg | 2022 | Prefilled syringe 6 mg/0.6 mL |
| Armlupeg | Pegfilgrastim-unne | Lupin/Valorum | Q5169 | Injection, pegfilgrastim-unne, (Armlupeg), biosimilar, 0.5 mg | Nov 2025 | Prefilled syringe 6 mg/0.6 mL |
Rolvedon (eflapegrastim-xnst) and Ryzneuta (efbemalenograstim alfa-vuxw) are long-acting G-CSF products but are not biosimilars to Neulasta; they carry separate J-codes (J1449 and J9361 respectively).
Billing units
All pegfilgrastim HCPCS codes use 0.5 mg as the billing unit. A standard 6 mg dose is billed as 12 units.
On-body injector coding
The Neulasta Onpro kit and Udenyca Onbody use the same J2506 and Q5111 codes respectively as their prefilled syringe counterparts. Per CMS billing guidance (MAC Article A54682), when the on-body injector is used, providers report the drug HCPCS code plus CPT 96377 (application of on-body injector, includes cannula insertion, for timed subcutaneous injection). The drug and the injector device are inclusive in the drug code.
ASP pricing: the pegfilgrastim inversion
The pegfilgrastim market exhibits a striking pricing anomaly: the reference product Neulasta has the lowest ASP, while several biosimilars carry substantially higher ASPs.
Q4 2025 ASP per 6 mg dose (CMS data)
| Product | ASP per 6 mg dose |
|---|---|
| Neulasta (J2506) | $239.76 |
| Ziextenzo (Q5120) | $296.50 |
| Nyvepria (Q5122) | $1,404.12 |
| Fulphila (Q5108) | $1,503.60 |
| Udenyca (Q5111) | $1,626.60 |
| Fylnetra (Q5130) | $2,202.00 |
| Stimufend (Q5127) | $3,579.60 |
Neulasta's ASP is more than 80% below the best-selling biosimilar Udenyca. This inversion results from Amgen aggressively discounting Neulasta to retain share, while biosimilar manufacturers maintain higher list prices offset by rebates and discounts that flow through the supply chain but are reflected in ASP only after a lag.
Why this matters for oncology clinics
Under Medicare Part B buy-and-bill, providers purchase the drug, administer it, and are reimbursed at ASP plus a percentage add-on. For reference products, the add-on is ASP + 6%. For qualifying biosimilars (those with ASP below the reference product), the add-on is ASP + 8% of the reference product's ASP.
This creates a counterintuitive dynamic: the absolute dollar margin on Neulasta (ASP ~$240 + 6% = ~$14 add-on) is far lower than on Udenyca (ASP ~$1,627 + 8% of Neulasta's $240 = ~$19 add-on, plus the spread between acquisition cost and ASP).
However, acquisition cost is the variable that determines whether a clinic is "underwater." If a manufacturer offers deep rebates that lower the net acquisition cost below the ASP used for reimbursement, the clinic profits. If rebates are insufficient, the clinic loses money on every dose.
Biosimilar market share vs. ASP
Despite Neulasta having the lowest ASP, biosimilar market share continues to grow:
| Product | Volume market share (Q2 2025) | ASP rank |
|---|---|---|
| Udenyca | ~39% | 4th highest |
| Fulphila | ~34% | 5th highest |
| Neulasta | ~13% | Lowest |
| Ziextenzo | ~3% | 2nd lowest |
| Nyvepria | ~3% | 3rd highest |
| Stimufend/Fylnetra | ~8% combined | Highest |
The disconnect between low-ASP products (Neulasta, Ziextenzo) and high market-share products (Udenyca, Fulphila) is driven by payer formulary preferences, GPO contracts, and rebate-driven positioning, not by reimbursement-margin optimization at the clinic level.
On-body injector: Neulasta Onpro vs. Udenyca Onbody
The on-body injector (OBI) is a co-packaged device that automatically delivers pegfilgrastim approximately 27 hours after a healthcare provider applies it to the patient's skin. This eliminates the need for the patient to return to the clinic the next day for injection.
Available OBI products
| Product | Status | HCPCS | Notes |
|---|---|---|---|
| Neulasta Onpro | Available | J2506 + CPT 96377 | Marketed since 2014; dominant OBI option |
| Udenyca Onbody | Available | Q5111 + CPT 96377 | FDA-approved December 2023; first biosimilar OBI |
Remaining OBI gaps
Six biosimilar pegfilgrastim products (Fulphila, Ziextenzo, Nyvepria, Stimufend, Fylnetra, Armlupeg) are available only as prefilled syringes for manual injection. Fresenius Kabi has reported developing a Stimufend OBI for potential 2025–2026 launch, but no FDA approval has been announced as of May 2026.
This gap matters for oncology practices that have built workflows around the Onpro device. Patients who need next-day automated delivery and whose payers prefer biosimilars may face access friction if Udenyca Onbody is not the preferred biosimilar on formulary.
Same-day administration
CMS MAC guidance (Palmetto GBA, Article A54682) allows the on-body injector to be applied on the same day as chemotherapy administration, as long as the device delivers the drug no less than 24 hours after cytotoxic chemotherapy. Providers must document the clinical rationale for same-day application, particularly patient/caregiver circumstances that create barriers to next-day clinic return.
Payer step-therapy hierarchies
Payer formularies create structured preferences among pegfilgrastim products that do not always track ASP economics. A 2025 analysis of eight major commercial plans found that no single pegfilgrastim product dominated coverage, and preferred products often carried higher ASPs than non-preferred alternatives.
Typical step-therapy structure (Health Net, Premera, Blue Shield of California)
First-line preferred: Fulphila or Udenyca (prefilled syringe)
Second-line: Other biosimilar pegfilgrastim products (Fylnetra, Nyvepria, Ziextenzo, Stimufend, Armlupeg) — patient must have tried and failed or had contraindications to first-line preferred products
Third-line (requires step through biosimilars first): Neulasta prefilled syringe, Neulasta Onpro, Rolvedon, Ryzneuta
Illinois step-therapy exemption
Illinois HB 5395, effective January 1, 2026, exempts oncology biosimilar step-therapy requirements unless the biosimilar is designated interchangeable by the FDA Purple Book. Since no pegfilgrastim biosimilar holds interchangeability designation as of May 2026, Illinois-regulated plans cannot require step therapy through biosimilars before covering Neulasta for oncology patients.
Medicare coverage
Medicare Part B covers pegfilgrastim under the buy-and-bill model. Coverage is not typically subject to step-therapy edits at the MAC level, though some MACs have published billing articles specifying that pegfilgrastim should be administered per FDA-approved dosing schedules and supported by appropriate ICD-10 diagnosis codes.
Coding and billing reference
Physician office (CMS-1500)
| Field | Entry |
|---|---|
| Box 21 (Diagnosis) | Appropriate ICD-10-CM code (e.g., Z79.02 chemotherapy encounter, D70.x neutropenia codes, C00–C96 malignancy codes) |
| Box 24D (Procedure) | Drug HCPCS (J2506 or Q5xxx) + Administration CPT (96372 for SC injection, or 96377 for OBI) |
| Box 24G (Units) | 12 units (for 6 mg dose at 0.5 mg billing unit) |
| JZ modifier | Append to drug HCPCS if no drug was discarded (single-dose vial/syringe) |
Hospital outpatient (UB-04)
| Field | Entry |
|---|---|
| Revenue code | 0636 (drugs requiring detailed coding) |
| HCPCS | J2506 or Q5xxx |
| Units | 12 (for 6 mg dose) |
| Date of service | Date of administration (or OBI application date) |
| NDC | Report 11-digit NDC for the specific product presentation |
Medicare add-on payment
Under the IRA's biosimilar incentive, qualifying biosimilars (those with ASP below the reference product) receive an enhanced add-on payment of ASP + 8% of the reference product's ASP for a 5-year period, compared to the standard ASP + 6% for reference products.
However, because Neulasta's ASP ($239.76) is already below most biosimilar ASPs, the enhanced add-on may not fully offset the higher acquisition cost of the biosimilar. The practical margin depends on each clinic's actual net acquisition cost after rebates and discounts.
Access and support programs
Neulasta (Amgen)
- Amgen Assist 360 (1-888-4ASSIST): benefits verification, PA support, appeals assistance
- Amgen Safety Net Foundation: patient assistance for uninsured/underinsured patients
- Co-pay assistance program for commercially insured patients
Udenyca (Coherus/Intas)
- Udenyca Support: benefits investigation, PA and appeals support
- Co-pay assistance for eligible commercially insured patients
- Bridge supply for patients facing PA delays
Fulphila (Biocon/Viatris)
- Viatris Patient Assistance Program: benefits verification and PA support
- Copay savings program for commercially insured patients
Stimufend (Fresenius Kabi)
- KabiCare: benefits verification, coding and reimbursement support, PA assistance
- Patient affordability program for eligible patients
Ziextenzo, Nyvepria, Fylnetra, Armlupeg
Each manufacturer offers its own hub services and patient support programs. Access teams should verify current program availability and eligibility criteria directly with the manufacturer, as programs may change.
What to monitor
- Armlupeg launch timing and formulary uptake: Lupin/Valorum's biosimilar received FDA approval in November 2025 and was assigned Q5169 effective 2026. Payer coverage decisions are pending.
- Stimufend OBI development: If Fresenius Kabi launches a Stimufend on-body injector, it would be only the third OBI option and could shift formulary dynamics.
- ASP convergence or divergence: Watch quarterly CMS ASP releases for whether Neulasta's aggressive pricing strategy continues to compress biosimilar ASPs or whether biosimilar manufacturers further discount to compete.
- IRA biosimilar incentive sunset: The 8% add-on payment for qualifying biosimilars applies for a 5-year period per biosimilar. Monitor whether this incentive meaningfully shifts prescribing behavior in pegfilgrastim.
- State step-therapy reform legislation: Illinois HB 5395 (effective 2026) is a model for oncology-specific step-therapy limits. If other states adopt similar provisions, payer formulary hierarchies may need adjustment.
- Reference pricing adoption: Given the wide ASP spread (Neulasta at $240 to Stimufend at $3,580 per dose), payers may increasingly adopt reference pricing for pegfilgrastim.
Sources
- CMS. "2026 HCPCS Application Summary, Quarter 1 2026, Drugs and Biologicals." Available at: https://www.cms.gov/files/document/2026-hcpcs-application-summary-quarter-1-2026-drugs-biologicals.pdf. Accessed May 2026.
- CMS Medicare Coverage Database. "Billing and Coding: Neulasta (pegfilgrastim) Onpro Kit / UDENYCA ONBODY (On-body Injector)." Article A54682. Available at: https://www.cms.gov/medicare-coverage-database/view/article.aspx?articleId=54682.
- CMS Medicare Coverage Database. "Pegfilgrastim (Fulphila; Neulasta; Neulasta Onpro; Nyvepria; Udenyca; Ziextenzo) J2506." Article A59126. Available at: https://www.cms.gov/medicare-coverage-database/view/article.aspx?articleid=59126.
- Samsung Bioepis. "Biosimilar Market Report Q4 2025." Available at: https://biologicshq.com/wp-content/uploads/2026/01/SB-Biosimilar-Market-Report-Q4-2025.pdf.
- Biosimilars Review & Report. "Pegfilgrastim Market Shares Don't Align With Net Prices. Is It Time for Reference Pricing?" January 23, 2025. Available at: https://biosimilarsrr.com/2025/01/23/why-the-distortion-in-the-pegfilgrastim-market.
- Big Molecule Watch. "FDA Approves Lupin's Pegfilgrastim Biosimilar, ARMLUPEG." December 8, 2025. Available at: https://www.bigmoleculewatch.com/2025/12/08/fda-approves-lupins-pegfilgrastim-biosimilar-armlupeg.
- Center for Biosimilars. "FDA Approves First Biosimilar for Neulasta Onpro." Available at: https://www.centerforbiosimilars.com/view/fda-approved-first-biosimilar-for-neulasta-onpro.
- Health Net. "Clinical Policy: Pegfilgrastim (Neulasta and biosimilars)." CP.PHAR.296. Available at: https://www.healthnet.com/content/dam/centene/policies/pharmacy-policies/phar/CP.PHAR.296.pdf.
- Premera Blue Cross. "Use of Granulocyte Colony-Stimulating Factors (G-CSF)." Policy 5.01.551. Available at: https://www.premera.com/medicalpolicies/5.01.551.pdf.
- OHSU Health Services. "Fulphila; Fylnetra; Neulasta; Nyvepria; Pegfilgrastim — Health System Medical Policy." November 2025. Available at: https://www.ohsu.edu/sites/default/files/2025-12/ohsu-hs-mps-gcsf-la-11-25.pdf.
- Fresenius Kabi. "Stimufend Coding and Reimbursement Guide." Available at: https://www.kabicare.us/wp-content/uploads/3500-STIMUFEND-Coding-and-Reimbursement-Guide.pdf.
- Amgen. "Neulasta Physician Office Coding and Billing Information Sheet." Available at: https://www.neulastahcp.com.
- JAMA-published analysis via PMC. "Pegfilgrastim Biosimilars in US Supportive Oncology: A Narrative Review." Available at: https://pmc.ncbi.nlm.nih.gov/articles/PMC9483396.
- PMC. "Biologic Drug Prices in Medicare Part B After Entry of Biosimilars to the Market." Available at: https://pmc.ncbi.nlm.nih.gov/articles/PMC12606378.
- Biosimilars Council. "How to Solve the Buy-and-Bill Biosimilar Pricing Puzzle?" August 2025. Available at: https://biosimilarscouncil.org/wp-content/uploads/2025/08/AAM-BC-How-to-Solve-the-Buy-and-Bill-Biosimilar-Pricing-Puzzle.pdf.
