Provider Briefing: The Neupogen (Filgrastim) Shortage in 2026

Filgrastim — marketed as Neupogen by Amgen and available through multiple biosimilar manufacturers — remains one of the most critical supportive care agents in oncology. As a granulocyte colony-stimulating factor (G-CSF), it's essential for reducing the risk of febrile neutropenia in patients receiving myelosuppressive chemotherapy, supporting bone marrow transplant recovery, and managing severe chronic neutropenia.

In 2026, intermittent supply disruptions continue to affect Filgrastim products nationwide. This briefing provides an overview of the shortage landscape, prescribing considerations, and practical tools to help your practice maintain uninterrupted G-CSF therapy for your patients.

Shortage Timeline

The Filgrastim shortage is not a single event but an ongoing pattern of intermittent disruptions:

• 2019–2020: Initial supply disruptions reported, primarily affecting brand Neupogen. Manufacturing issues at Amgen's production facilities cited as a contributing factor.
• 2021–2022: Broader supply chain disruptions, partly related to pandemic-era logistics challenges, affected multiple Filgrastim products. The FDA placed several Filgrastim products on its shortage list.
• 2022: Releuko (Filgrastim-ayow) received FDA approval, adding a third biosimilar to the market.
• 2023–2024: Supply stabilized somewhat with increased biosimilar availability. Nypozi (Filgrastim-szfi) approved in 2024, further diversifying the market.
• 2025–2026: Intermittent regional shortages persist. Specific formulations and strengths remain periodically unavailable. Overall market supply improved but not fully resolved.

Prescribing Implications

The shortage has several practical implications for prescribers:

Biosimilar Substitution

With four FDA-approved Filgrastim biosimilars on the market — Zarxio (Filgrastim-sndz), Nivestym (Filgrastim-aafi), Releuko (Filgrastim-ayow), and Nypozi (Filgrastim-szfi) — there is considerable flexibility for product substitution. All have demonstrated biosimilarity to Neupogen in rigorous clinical trials.

Key considerations:

• Most state pharmacy laws now permit pharmacist-initiated biosimilar substitution for interchangeable products. Verify your state's specific regulations.
• Writing prescriptions for "Filgrastim" rather than a specific brand allows pharmacists maximum flexibility to dispense whatever product is in stock.
• Patient education is important — some patients may be concerned about receiving a different brand. Reassure them that biosimilars have the same active ingredient, dosing, and clinical effects.

Long-Acting G-CSF Alternatives

When short-acting Filgrastim products are unavailable, consider switching eligible patients to Pegfilgrastim (Neulasta) or one of its biosimilars (Udenyca, Nyvepria, Fylnetra, Stimufend). Benefits include:

• Once-per-cycle dosing improves adherence and reduces pharmacy touchpoints
• Different supply chain — Pegfilgrastim products may be available when Filgrastim is not
• Established efficacy in prophylaxis of chemotherapy-induced febrile neutropenia

Note that Pegfilgrastim is not interchangeable with Filgrastim for all indications. It is not approved for mobilization of peripheral blood progenitor cells or for severe chronic neutropenia.

Buy-and-Bill vs. Pharmacy Benefit

For practices that purchase and administer G-CSF in the office setting (buy-and-bill model), sourcing may differ from retail pharmacy channels. Consider:

• Working with specialty distributors who maintain dedicated oncology supply
• Maintaining relationships with multiple wholesalers to improve access during shortages
• Monitoring ASP (Average Sales Price) reimbursement rates to ensure financial viability of stocking biosimilars

Current Availability Picture

Availability varies significantly by:

• Product: Biosimilars generally have better supply than brand Neupogen
• Formulation: Prefilled syringes may be more readily available than vials, or vice versa
• Strength: The 480 mcg strength has historically been more affected than the 300 mcg
• Channel: Specialty distributors and hospital pharmacies may have better access than retail chains
• Region: Supply varies geographically; some regions are consistently better stocked

Medfinder for Providers offers real-time pharmacy stock data that can help your practice and patients identify where Filgrastim products are currently available.

Cost and Access Considerations

Cost remains a significant patient access barrier:

• Brand Neupogen: Approximately $300–$450 per injection (cash price)
• Filgrastim biosimilars: $200–$350 per injection — a 15–30% reduction
• Full treatment course: $3,000–$10,000+ per chemotherapy cycle at cash prices
• Insurance: Most commercial plans and Medicare cover Filgrastim products, but prior authorization is common, and preferred product lists may not align with what's actually available

When a patient's preferred product is unavailable, insurance navigation can cause delays. Proactive communication with payers — and familiarity with each plan's formulary — can help minimize disruptions.

Patient Assistance Resources

• Amgen Safety Net Foundation: Provides free Neupogen for uninsured or underinsured patients (income ≤400% FPL)
• Patient Access Network (PAN) Foundation: Co-pay assistance for cancer supportive care
• HealthWell Foundation: Financial assistance for eligible patients
• NeedyMeds / RxAssist: Comprehensive databases of assistance programs

Tools and Resources for Your Practice

• Medfinder for Providers: Real-time Filgrastim availability search across pharmacies — helps patients and staff locate in-stock products quickly
• FDA Drug Shortage Database: Official shortage information and estimated resolution dates
• ASHP Drug Shortage Resource Center: Clinical guidance on managing drug shortages
• NCCN Clinical Practice Guidelines: Evidence-based recommendations for G-CSF use, including guidance on biosimilar use

Looking Ahead

Several trends suggest the Filgrastim supply situation will continue to improve:

• Expanding biosimilar market: Four biosimilars now compete with brand Neupogen, creating supply redundancy
• Manufacturer investment: Biosimilar manufacturers are scaling production capacity
• Policy changes: Increased biosimilar substitution authority at the state level, and payer policies increasingly favoring biosimilars, should improve product fluidity
• Practice adaptation: More oncology practices are building multi-product G-CSF formularies rather than relying on a single product

However, the fundamental fragility of biologic manufacturing means that isolated shortages will likely continue to occur. Building flexibility into your practice's G-CSF prescribing — and knowing where to look when shortages hit — remains essential.

Final Thoughts

The Neupogen shortage is a manageable challenge with the right tools and approach. Prescribing broadly (Filgrastim rather than a specific brand), maintaining biosimilar familiarity, leveraging in-office administration, and using real-time availability tools like Medfinder for Providers can help ensure your patients don't miss critical G-CSF therapy.

For patient-facing resources you can share, see our posts on how to find Neupogen in stock and Neupogen alternatives. For guidance on helping patients with costs, visit our provider's guide to Neupogen cost savings.