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Research Report

Published: Aug 29, 2025

Fianlimab (REGN3767): A Comprehensive Clinical and Strategic Analysis of a Novel LAG-3 Inhibitor in Oncology

Executive Summary

Fianlimab (REGN3767) is an investigational, high-affinity, fully human monoclonal antibody that targets the Lymphocyte Activation Gene-3 (LAG-3) immune checkpoint. Developed by Regeneron Pharmaceuticals, fianlimab represents a significant advancement in the field of immuno-oncology and is being evaluated primarily in combination with the anti-PD-1 antibody cemiplimab (Libtayo®). This combination aims to provide a more potent and comprehensive reversal of T-cell exhaustion, a key mechanism of tumor immune evasion, than is achievable with anti-PD-1 monotherapy.

The core thesis of this report is that fianlimab, based on compelling early-phase clinical data, is positioned as a potential best-in-class LAG-3 inhibitor. Its extensive clinical development program is strategically engineered not only to secure market entry but to challenge and potentially displace existing standards of care. This includes the first-to-market LAG-3/PD-1 combination, Opdualag™ (relatlimab and nivolumab), through a high-reward strategy of demonstrating clinical superiority in direct, head-to-head pivotal trials.

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Clinical Trials

Title	Posted	Study ID	Phase	Status	Sponsor
A Randomized Trial of Fianlimab and Cemiplimab +/- Ipilimumab or Ipilimumab Plus Nivolumab in First-line Advanced Renal Cell Carcinoma (RCC)	2025/09/23	NCT07188896	Not Applicable	Not yet recruiting	Brian Rini
Cemiplimab and Fianlimab Before Surgery for the Treatment of Stage IB-IIIB Non-Small Cell Lung Cancer	2025/04/09	NCT06918132	Phase 2	Recruiting	Mayo Clinic
Thoracic Radiotherapy and Inhibition of PD-1 and LAG-3 for Locally Advanced Non-Small Cell Lung Cancer	2025/03/07	NCT06865339	Phase 2	Recruiting	Nitin Ohri
Investigation of Ubamatamab Combination Therapy in Adult Participants With Platinum-Resistant Ovarian Cancer	2025/01/22	NCT06787612	Phase 2	Recruiting	Regeneron Pharmaceuticals
A Study of Cemiplimab and Fianlimab in People With Clear Cell Renal Cell Carcinoma	2024/11/21	NCT06699602	Phase 2	Recruiting	Memorial Sloan Kettering Cancer Center
A Study of Fianlimab, Cemiplimab, and Ipilimumab in People With Melanoma	2024/09/19	NCT06594991	Phase 2	Recruiting	Memorial Sloan Kettering Cancer Center
A Study of Gemcitabine/Cisplatin Plus Cemiplimab (REGN2810, Anti-PD-1) With or Without Fianlimab (REGN3767, Anti-LAG-3) in Patients With Localized Muscle-invasive Bladder Cancer (NeoSTOP-IT)	2024/08/26	NCT06571708	Phase 2	Recruiting	Columbia University
Study of Cemiplimab Alone or in Combination With Fianlimab and/or Other Experimental Agents in Adult Participants With Peri-operative Stage III/IV Cutaneous Squamous Cell Carcinoma (CSCC)	2024/04/25	NCT06384820	Phase 2	Withdrawn	Regeneron Pharmaceuticals
A Study With Combinations of Anti-LAG-3 and Anti-PD-1 Antibodies in Adult Participants With Advanced or Metastatic Melanoma (Harmony Head-to-Head)	2024/02/07	NCT06246916	Phase 3	Recruiting	Regeneron Pharmaceuticals
Cemiplimab With or Without Fianlimab to Treat Older Patients With Localized or Locally Advanced MSI-H Colorectal Cancer	2024/01/16	NCT06205836	Phase 2	Recruiting	Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins

FDA Drug Approvals

Approved Product	Manufacturer	NDC Code	Route	Strength	Effective Date
No FDA approvals found for this drug.

EMA Drug Approvals

Approved Product	Authorization Holder	Status	Issued Date
No EMA approvals found for this drug.

HSA Drug Approvals

Approved Product	Manufacturer	Approval Number	Dosage Form	Strength	Approval Date
No HSA approvals found for this drug.

NMPA Drug Approvals

Approved Product	Company	Approval Number	Drug Type	Dosage Form	Approval Date
No NMPA approvals found for this drug.

PPB Drug Approvals

Approved Product	Registration No.	Company	Licence No.	Strength	Registration Date
No PPB approvals found for this drug.

TGA Drug Approvals

Approved Product	ARTG ID	Sponsor	Registration Type	Status	Registration Date
No TGA approvals found for this drug.

Health Canada Drug Approvals

Approved Product	Company	DIN	Dosage Form	Strength	Market Date
No Health Canada approvals found for this drug.

CIMA AEMPS Drug Approvals

Approved Product	Company	Registration Number	Pharmaceutical Form	Prescription Type	Status
No CIMA AEMPS (Spain) approvals found for this drug.

Philippines FDA Drug Approvals

Approved Product	Company	License Number	Dosage Form	Strength	Approval Date
No Philippines FDA approvals found for this drug.

Saudi SFDA Drug Approvals

Approved Product	Company	License Number	Dosage Form	Strength	Approval Date
No Saudi SFDA approvals found for this drug.

Malaysia NPRA Drug Approvals

Approved Product	Company	Registration Number	Dosage Form	Strength	Approval Date
No Malaysia NPRA approvals found for this drug.

UK EMC Drug Information

Medicine Name	MA Holder	MA Number	Pharmaceutical Form	Active Ingredient	Authorization Date
No UK EMC drug information found for this drug.

Related News

LAG-3 Immunotherapies Market Poised for Explosive Growth with Next-Generation Therapies Advancing Across Major Markets

8 months ago

• The LAG-3 next-generation immunotherapies market is projected to grow from $463.6 million in 2024 to $5.5 billion by 2035, driven by increasing solid tumor cases and expanding treatment options. • Bristol Myers Squibb's Opdualag (nivolumab/relatlimab) has established a foundation for LAG-3 therapies, with promising candidates from Merck, Regeneron, and Immutep advancing through clinical trials. • Biomarker-driven precision medicine and strategic regulatory support are accelerating development of novel LAG-3 therapies, including monoclonal antibodies, bispecific antibodies, and soluble LAG-3 molecules.

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• Pfizer is prioritizing its oral obesity drug, danuglipron, with late-stage studies planned for the second half of 2025, aiming for a novel mechanism of action. • Regeneron anticipates Phase III data readouts for itepekimab in COPD and fianlimab in melanoma, potentially expanding its portfolio alongside Dupixent. • BioNTech is advancing its mRNA-based cancer immunotherapies, including BNT327/PM8002 for solid tumors and BNT323/DB-1303, an ADC for endometrial cancer. • Sarepta Therapeutics reported strong initial sales for Elevidys in Duchenne muscular dystrophy and is pursuing a Phase III trial for limb-girdle muscular dystrophy.

Libtayo Demonstrates Significant Disease-Free Survival Improvement in High-Risk CSCC

10 months ago

• Phase 3 C-POST trial reveals adjuvant Libtayo (cemiplimab) significantly improves disease-free survival (DFS) in high-risk cutaneous squamous cell carcinoma (CSCC) patients after surgery. • Libtayo reduced the risk of disease recurrence or death by 68% compared to placebo, with a hazard ratio of 0.32 (95% CI: 0.20-0.51; p<0.0001) at interim analysis. • Regeneron plans to submit these results to the FDA in the first half of 2025, potentially expanding Libtayo's use in adjuvant settings. • Cemiplimab sales exceeded $1 billion in 2024, solidifying its position as a foundational element in Regeneron's oncology portfolio.

Novel Therapies Show Promise in Melanoma, Breast, and Prostate Cancers

a year ago

Fianlimab plus cemiplimab demonstrates durable efficacy and a better-tolerated safety profile compared to ipilimumab and nivolumab in advanced melanoma, showing promise in ongoing adjuvant and frontline metastatic studies.

Fianlimab Plus Cemiplimab Shows Durable Activity in Advanced Melanoma