Regeneron Pharmaceuticals Details C5 Strategy, With PNH Data Due Q4 and gMG NDA Under Review

Key Points

• Regeneron’s C5 strategy pairs an siRNA (cemdisiran) that lowers hepatic C5 production with an antibody (pozelimab) that neutralizes circulating C5, allowing the company to “match the biology” and deliver tunable complement inhibition (partial or near‑complete) across PNH, gMG and GA.
• Clinical catalysts and results: Cohort B enrollment in the registrational PNH ACCESS program is complete with a data readout expected in Q4, and cemdisiran met primary and key secondary endpoints in the phase III NIMBLE gMG trial, showing clinically meaningful, sustained benefit and a favorable safety profile.
• Commercial outlook: Regeneron views the C5 franchise as a multi‑indication, multi‑billion‑dollar opportunity with gMG as the near‑term priority (potential FDA decision/launch in Q4 2026), plans quarterly subcutaneous dosing with eventual self‑administration, and will commercialize while paying modest royalties to Alnylam.

Regeneron Pharmaceuticals NASDAQ: REGN outlined its C5 complement development strategy in an investor roundtable focused on cemdisiran, an siRNA targeting C5, and pozelimab, a C5-targeting antibody already approved for an ultra-rare disease. Executives emphasized a “match the biology” approach—using cemdisiran alone, pozelimab alone, or the combination—to deliver different depths of complement inhibition across multiple indications, including paroxysmal nocturnal hemoglobinuria (PNH), generalized myasthenia gravis (gMG), and geographic atrophy (GA).

Program overview: siRNA plus antibody to tune C5 inhibition

Ryan Crowe, senior vice president of investor relations, said the C5 effort is one of five late-stage programs Regeneron believes are positioned to deliver “meaningful advances” over the next several years. He highlighted multiple upcoming catalysts, including registrational PNH data expected in the fourth quarter of this year, an FDA decision on cemdisiran in gMG expected in the fourth quarter (following a recently submitted NDA using a priority review voucher), and initial phase III lead-in data in GA anticipated late this year.

George Yancopoulos, Regeneron’s board co-chair, president, and chief scientific officer, said the company’s approach represents the first time an antibody and an siRNA have been combined to inhibit the same pathway. He explained that cemdisiran reduces C5 production in the liver, while pozelimab neutralizes residual circulating C5, enabling “complete” blockade when used together. The two-agent design, he said, provides flexibility to deliver partial inhibition where appropriate and near-complete, uninterrupted inhibition where required.

PNH: Phase III ACCESS trial progresses; Cohort B enrollment complete

Andres Sirulnik, senior vice president and clinical development unit head for hematology, described PNH as a life-threatening hematologic disorder driven by uncontrolled C5 activation, with complications including hemolysis and thrombosis. While current therapies improve survival, he said many patients do not fully normalize lactate dehydrogenase (LDH) or experience breakthrough hemolysis, and those with extravascular hemolysis can remain underserved.

Sirulnik reviewed the phase III ACCESS I program, which includes a head-to-head comparison of cemdisiran plus pozelimab versus ravulizumab in Cohort A and versus eculizumab in the registrational Cohort B. Regeneron announced on the call that enrollment in Cohort B is complete, setting up a “registration-enabling data readout” in the fourth quarter of this year.

He also highlighted 26-week results from exploratory Cohort A (previously reported in late 2024). According to Sirulnik, nearly all patients treated with the combination achieved normal LDH levels, with average LDH at 0.8 times the upper limit of normal at week 26 and 96% maintaining adequate control of hemolysis, compared with ravulizumab at 1.2 times the upper limit of normal and 80% maintaining adequate control. In an extension phase where ravulizumab patients switched to the combination, he said LDH control improved, including in patients who had not achieved control on ravulizumab.

Regeneron also disclosed it has initiated a first-in-human study of an siRNA targeting complement factor B, initially aimed at PNH patients who remain anemic despite optimal C5 therapy due to extravascular hemolysis, with potential broader applications.

gMG: Phase III NIMBLE supports quarterly subcutaneous cemdisiran

Umesh Chaudhari, vice president and global program head of C5, said gMG is driven by complement-mediated structural injury at the neuromuscular junction, which is why C5 inhibition has shown clinical efficacy. He positioned cemdisiran as a potential way to deliver sustained disease control with reduced treatment burden.

Chaudhari described the phase III NIMBLE trial as a randomized, double-blind, placebo-controlled study in acetylcholine receptor-positive patients on stable background therapy, with cemdisiran administered subcutaneously every 12 weeks during the 24-week placebo-controlled period. He said cemdisiran monotherapy met the primary endpoint (change from baseline in MG-ADL at week 24) and all key secondary endpoints, delivering a 2.3-point placebo-adjusted improvement in MG-ADL that was “clinically meaningful and statistically significant.” The key secondary endpoint (QMG) was met with a 2.8-point placebo-adjusted improvement. He added that efficacy appeared as early as week two and was sustained without evidence of waning between doses.

While a combination arm also met endpoints, Chaudhari said it did not provide additional benefit over cemdisiran monotherapy, supporting Regeneron’s view that gMG may not require complete complement blockade.

On safety, Chaudhari said cemdisiran monotherapy was generally well tolerated through 24 weeks, with no serious infections, no meningococcal infections, and no treatment discontinuations during the double-blind period. He noted adverse event rates were numerically lower versus placebo and combination therapy, and said only 1% of patients in the cemdisiran cohort experienced the adverse event of myasthenia gravis, compared with 17% on placebo.

Geographic atrophy: systemic C5 inhibition aims to reduce burden and address safety concerns

Sirulnik said GA is an irreversible form of dry age-related macular degeneration with substantial functional impact, and that while intravitreal complement-inhibiting therapies have been approved, unmet need remains because they have not prospectively demonstrated preservation or improvement of visual function and require frequent injections with “meaningful ocular safety risks.”

Regeneron’s phase III SIENA trial is evaluating systemic C5 inhibition in GA secondary to AMD in approximately 975 patients, structured as a seamless two-cohort program. Sirulnik said Cohort A is fully enrolled, with interim data expected in the fourth quarter of 2026. He described Cohort A as a “decision-enabling checkpoint” rather than a regulatory readout and said it will help determine whether monotherapy or combination therapy is needed.

In Q&A, Yancopoulos said Regeneron’s GA studies are powered to detect a potential functional benefit and argued that a systemic subcutaneous approach could reduce treatment burden, particularly for bilateral disease and for patients who also require anti-VEGF therapy. He also pointed to concerns about occlusive retinal vasculitis reported with current intravitreal agents and said Regeneron would expect not to see that risk with systemic administration.

When asked about prior data from an eculizumab GA study, Sirulnik cited the small size of the investigator-initiated COMPLETE study and said the eculizumab dosing used “does not provide full suppression of terminal complement activity.” Yancopoulos added that Regeneron is not expecting a larger lesion-growth slowing than intravitreal agents, but rather similar slowing “in a much more convenient and safer manner,” referencing an approximately 20% slowing as the benchmark discussed on the call.

Sirulnik also said Regeneron is developing an intravitreal pozelimab formulation, citing potential durability, a possible safety advantage from a non-PEGylated antibody, and the potential for co-formulation with anti-VEGF therapy.

Commercial outlook: gMG near-term focus; multi-indication strategy

Soma Gupta, vice president of commercial new products, said Regeneron views the C5 program as a “multi-indication, multi-billion-dollar opportunity” across gMG, PNH, and GA, stating that the three markets combined generate about $9 billion in annual worldwide sales. She said Regeneron is solely responsible for development, manufacturing, and commercialization for cemdisiran and the combination, while paying “modest royalties on net sales” to Alnylam.

Gupta called gMG the first and largest near-term opportunity and said Regeneron expects an FDA decision and potential launch in the fourth quarter of 2026. She added that advanced therapy penetration in gMG is about 15% today and is expected to rise toward 40% over time. Gupta said Regeneron plans to position cemdisiran as a differentiated targeted therapy based on durability, efficacy, safety, and quarterly subcutaneous dosing, with uptake expected to come from both switches and new starts. She also said the company aims to evolve from in-office subcutaneous administration to self-administration over time, with timing dependent on regulatory interactions.

Yancopoulos closed by reiterating that Regeneron views the C5 effort as “not a single asset story,” emphasizing the ability to tailor the level of complement inhibition by indication. He said the company believes the program represents an “underappreciated opportunity” for long-term growth, with near-term pivotal data and planned launches across multiple diseases.

About Regeneron Pharmaceuticals NASDAQ: REGN

Regeneron Pharmaceuticals, Inc NASDAQ: REGN is a U.S.-based biotechnology company founded in 1988 and headquartered in Tarrytown, New York. It focuses on discovering, developing, manufacturing and commercializing medicines for serious medical conditions. The company combines laboratory research, clinical development and in-house manufacturing to advance a pipeline of biologic therapies across multiple therapeutic areas.

Regeneron is known for its proprietary drug discovery technologies, including its VelocImmune platform, which is used to generate fully human monoclonal antibodies.

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