Sponsor: Brian Rini (other)
Phase: 2
Start date: Sept. 23, 2025
Planned enrollment: 120
Fianlimab (REGN3767) is an investigational, fully human, hinge-stabilized IgG4 monoclonal antibody targeting lymphocyte activation gene-3 (LAG-3). It is being developed primarily with the anti–PD-1 antibody cemiplimab. As of September 22, 2026, fianlimab remains unapproved, and its strongest clinical evidence is in advanced melanoma. (aacrjournals.org)
LAG-3 is an inhibitory immune-checkpoint receptor expressed on activated T cells. Fianlimab binds LAG-3 and blocks its interaction with MHC class II, thereby reducing inhibitory signaling and restoring T-cell activation. Preclinical models showed greater antitumor activity when LAG-3 blockade was combined with cemiplimab-mediated PD-1 blockade. Its Fc region was engineered to minimize antibody-dependent cytotoxicity against LAG-3-expressing immune cells. (aacrjournals.org)
In a published phase 1 study, 98 patients with advanced melanoma who had not received anti–PD-1 therapy for advanced disease had an investigator-assessed objective response rate (ORR) of 61.2% with fianlimab plus cemiplimab and a median progression-free survival (PFS) of 13.3 months after 12.6 months’ median follow-up. ORRs were 63% in anti–PD-1-naïve patients, 63% in systemic-treatment-naïve patients, and 56% in patients previously treated in the neoadjuvant or adjuvant setting. Among 15 patients previously treated with anti–PD-1 therapy for advanced disease, ORR was 13.3% and median PFS was 1.5 months. (pubmed.ncbi.nlm.nih.gov)
Longer follow-up of the 98-patient population, reported in a 2026 conference proceeding, found a blinded-independent-review ORR of 57%, including a 25% complete-response rate; median PFS was 24 months, while median overall survival had not been reached. These single-arm findings require interpretation alongside randomized evidence. (scholarlycommons.henryford.com)
In a 1,546-patient randomized phase 3 trial in previously untreated unresectable or metastatic melanoma, neither tested dose of fianlimab plus cemiplimab significantly improved PFS over pembrolizumab. Median PFS was 11.5 months with high-dose fianlimab, 9.6 months with low-dose fianlimab, and 6.4 months with pembrolizumab. For the high-dose comparison, the hazard ratio was 0.845 (95% CI 0.709–1.008; p=0.0627). These results were disclosed by the manufacturer in May 2026 and had not yet been presented as a peer-reviewed publication in the sources reviewed. (investor.regeneron.com)
In the published melanoma phase 1 study, grade 3 or higher treatment-emergent adverse events occurred in 44% of anti–PD-1-naïve patients, while grade 3 or higher treatment-related events occurred in 22%. Common events included fatigue, nausea, diarrhea, rash and pruritus. Adrenal insufficiency occurred in 12% overall and was grade 3–4 in 4%, a higher incidence than generally reported with PD-1 monotherapy. Treatment-related adverse events caused discontinuation in 13%; two treatment-related deaths were reported. (pmc.ncbi.nlm.nih.gov)
The phase 3 announcement stated that no new safety signals were identified, but detailed safety results were not provided. (investor.regeneron.com)
Last updated: Sep 2026
Goal: Evaluate whether adding investigational LAG-3 blockade with fianlimab to PD-1 blockade, with or without ipilimumab, improves first-line outcomes in advanced clear-cell renal cell carcinoma compared with standard ipilimumab plus nivolumab.
Patients: Adults with previously untreated, unresectable locally advanced or metastatic renal cell carcinoma containing a clear-cell component, across all IMDC risk groups. Patients need measurable disease, Karnofsky performance status of at least 70%, adequate organ function, and available tumor tissue. Key exclusions include prior systemic RCC therapy, active autoimmune disease requiring systemic immunosuppression, a history of myocarditis, and ongoing prednisone-equivalent dosing of at least 10 mg/day.
Design: Three-arm, randomized phase 2 trial with 2:2:1 allocation to the triplet, doublet, or active-control arm, respectively.
Treatments: Arm A receives intravenous fianlimab, cemiplimab, and ipilimumab; Arm B receives intravenous fianlimab and cemiplimab. Fianlimab is an investigational anti-LAG-3 antibody that blocks an inhibitory T-cell checkpoint and is being paired with the anti-PD-1 antibody cemiplimab. In a single-arm phase 1 melanoma study, the combination produced a 61.2% objective response rate among patients without prior anti-PD-1 treatment for advanced disease; however, a subsequent randomized phase 3 melanoma trial did not show a statistically significant progression-free survival benefit over pembrolizumab, and efficacy in RCC remains unknown. Arm C receives intravenous ipilimumab plus nivolumab, a standard CTLA-4/PD-1 checkpoint-inhibitor regimen.
Outcomes: The primary endpoint is confirmed objective response rate by RECIST 1.1 over 2 years. Secondary endpoints include median, 12-month, and 24-month progression-free survival; duration of response; treatment-free survival, including time with grade 3 or higher treatment-related toxicity; and treatment-related adverse events and serious adverse events.
Burden on patient: Moderate. All arms require repeated visits for intravenous therapy, laboratory monitoring, and imaging to assess response and toxicity. Available tumor tissue is required, preferably from a recent metastatic lesion, which may necessitate a biopsy if suitable tissue is unavailable; no routine serial research biopsies or intensive pharmacokinetic sampling are specified. Travel and monitoring demands may be greater than with oral therapy, but much of the assessment resembles usual care for intravenous immunotherapy.
Last updated: Sep 2026
Inclusion Criteria:
1. Signed informed consent and HIPAA authorization for release of personal health information prior to registration. NOTE: HIPAA authorization may be included in the informed consent or obtained separately.
2. Age ≥ 18 years at the time of consent.
3. Karnofsky Performance Status ≥ 70% within 14 days prior to registration.
4. Histological or cytological evidence of renal cell carcinoma having a clear cell component
5. Advanced (not amenable to curative surgery or radiation therapy) or metastatic (AJCC Stage IV \[version 9\]) renal cell carcinoma.
6. Treatment naïve for systemic therapy for renal cell carcinoma including no prior neo/adjuvant systemic therapy
7. Measurable disease according to RECIST 1.1 within 28 days prior to registration.
8. Patient must have either a formalin-fixed, paraffin-embedded (FFPE) tissue block or unstained tumor tissue sections, obtained from preferably a metastatic lesion, preferably within 3 months or no more than 12 months with an associated pathology report. If the metastatic lesion biopsy specimen does not contain at least 20 unstained slides, supplementation with primary kidney cancer tissue is acceptable.
9. Demonstrate adequate organ function as defined in the protocol. All screening labs to be obtained within 14 days prior to registration.
10. Females of childbearing potential must have a negative serum pregnancy test within 14 days prior to registration.
11. Females of childbearing potential who are sexually active with a male able to father a child must be willing to abstain from penile-vaginal intercourse or must use an effective method(s) of contraception. Males able to father a child who are sexually active with a female of childbearing potential must be willing to abstain from penile-vaginal intercourse or use an effective method(s) of contraception.
12. Known HIV-infected subjects on effective anti-retroviral therapy with undetectable viral load and CD4 count above 350 either spontaneously or on a stable antiviral regimen within 6 months of registration are eligible for this trial. Testing is not required at screening unless mandated by local policy
13. Subjects with known chronic hepatitis B virus (HBV) infection, must have an undetectable HBV viral load (serum hepatitis B virus DNA PCR that is below the limit of detection) and be on suppressive therapy, if indicated.
14. Subjects with a history of hepatitis C virus (HCV) infection must have been treated and cured (undetectable HCV RNA by PCR either spontaneously or in response to a successful prior course of anti-HCV therapy). For subjects with HCV infection who are currently on treatment, the HCV viral load must be undetectable to be eligible for this trial. Testing is not required at screening unless mandated by local policy.
15. As determined by the enrolling physician or protocol designee, ability of the subject to understand and comply with study procedures for the entire length of the study.
Exclusion Criteria:
1. Prior systemic therapy against renal cell carcinoma in the neo/adjuvant or metastatic setting
2. Any condition requiring ongoing ≥ 10 mg prednisone equivalent/day
3. Participants with a history of myocarditis.
4. If clinically indicated based on clinical assessment and any ECG abnormalities, optional troponin T (TnT) or troponin I (TnI) may be done as described in the protocol.
5. Ongoing or recent (within 2 years) evidence of an autoimmune disease that required systemic treatment with immunosuppressive agents. The following are allowed: vitiligo, childhood asthma that has resolved, residual hypothyroidism that requires only hormone replacement, psoriasis not requiring systemic treatment.
6. Central nervous system (CNS) metastases as described in the protocol.
7. Active infection requiring systemic therapy as described in the protocol.
8. Pregnant or breastfeeding as described in the protocol.
9. Prior or concurrent malignancy whose natural history or treatment has the potential to interfere with the safety or efficacy assessment of the investigational regimen, per treating physician discretion.
10. Subjects must not receive live attenuated vaccines within 4 weeks prior to Cycle 1 Day 1 or at any time during the study. Inactivated vaccines are allowed.
11. Known hypersensitivity to the active substances or to any of the excipients.
12. Currently participating in another study or participated in any study of an investigational agent or investigational device within 30 days of the first dose of study drug.
Nashville, Tennessee, 37232, United States
[email protected] / 615-343-6584
Status: Recruiting