On August 18, 2023 Merck (NYSE: MRK), known as MSD outside of the United States and Canada, reported topline results from LITESPARK-005, the first positive Phase 3 trial investigating WELIREG, Merck’s oral hypoxia-inducible factor-2 alpha (HIF-2α) inhibitor (Press release, Merck & Co, AUG 18, 2023, View Source [SID1234634501]). LITESPARK-005 is evaluating WELIREG for the treatment of adult patients with advanced renal cell carcinoma (RCC) that has progressed following PD-1/L1 checkpoint inhibitor and vascular endothelial growth factor-tyrosine kinase inhibitor (VEGF-TKI) therapies. In the trial, WELIREG showed a statistically significant and clinically meaningful improvement in progression-free survival (PFS) compared to everolimus, based on a pre-specified interim analysis conducted by an independent Data Monitoring Committee. A statistically significant improvement in the trial’s key secondary endpoint of objective response rate (ORR) was also demonstrated. A trend toward improvement in overall survival (OS), a dual primary endpoint, was observed; however, this result did not reach statistical significance. OS will be tested at a subsequent analysis. The safety profile of WELIREG in this trial was consistent with that observed in previously reported studies. Results will be presented at an upcoming medical meeting and shared with regulatory authorities.
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"Patients with advanced RCC face low survival rates, and for those whose cancer progresses following PD-1/L1 and VEGF-TKI therapies, there is a need for new treatment options that can reduce their risk of disease progression or death," said Dr. Marjorie Green, senior vice president and head of late-stage oncology, global clinical development, Merck Research Laboratories. "This is the first Phase 3 trial to show positive results in advanced RCC following these therapies and the first new mechanism to demonstrate potential in advanced RCC in recent years. We look forward to discussing these results with health authorities."
WELIREG was the first HIF-2α inhibitor therapy approved in the U.S. and is currently approved in the U.S., Great Britain, Canada and several other countries for the treatment of adult patients with von Hippel-Lindau (VHL) disease who require therapy for associated RCC, central nervous system hemangioblastomas, or pancreatic neuroendocrine tumors, not requiring immediate surgery, based on ORR and duration of response (DOR) data from the Phase 2 LITESPARK-004 trial. Additional applications are currently under regulatory agency review worldwide based on LITESPARK-004.
LITESPARK-005 is part of a comprehensive development program for WELIREG comprised of four Phase 3 trials in RCC, including LITESPARK-011 and LITESPARK-012, evaluating WELIREG in the second-line and treatment-naïve advanced disease settings, and LITESPARK-022, evaluating WELIREG in the adjuvant setting.
About LITESPARK-005
LITESPARK-005 is a randomized, open-label Phase 3 trial (ClinicalTrials.gov, NCT04195750) evaluating WELIREG compared to everolimus for the treatment of patients with advanced RCC that has progressed after prior treatment with PD-1/L1 and VEGF-TKI therapies, in sequence or in combination. The dual primary endpoints are PFS and OS. Secondary endpoints include ORR, DOR and safety and tolerability. The trial enrolled 746 patients who were randomized to receive WELIREG (120 mg orally once daily) or everolimus (10 mg orally once daily).
About renal cell carcinoma
Renal cell carcinoma is by far the most common type of kidney cancer; about nine out of 10 kidney cancer diagnoses are RCCs. Renal cell carcinoma is about twice as common in men than in women. Most cases of RCC are discovered incidentally during imaging tests for other abdominal diseases. In the U.S., approximately 15% of patients with kidney cancer are diagnosed at an advanced stage.
About WELIREG (belzutifan) 40 mg tablets, for oral use
Indication in the U.S.
WELIREG (belzutifan) is indicated for the treatment of adult patients with von Hippel-Lindau (VHL) disease who require therapy for associated renal cell carcinoma (RCC), central nervous system (CNS) hemangioblastomas, or pancreatic neuroendocrine tumors (pNET), not requiring immediate surgery.
Selected Safety Information for WELIREG
Warning: Embryo-Fetal Toxicity
Exposure to WELIREG during pregnancy can cause embryo-fetal harm. Verify pregnancy status prior to the initiation of WELIREG. Advise patients of these risks and the need for effective non-hormonal contraception as WELIREG can render some hormonal contraceptives ineffective.
Anemia
WELIREG can cause severe anemia that can require blood transfusion. In Study 004, anemia occurred in 90% of patients and 7% had Grade 3 anemia. Median time to onset of anemia was 31 days (range: 1 day to 8.4 months). In Study 001, a clinical trial in patients with advanced solid tumors (n=58) treated at the recommended dose, anemia occurred in 76% of patients and 28% had Grade 3 anemia.
Monitor for anemia before initiation of and periodically throughout treatment. Closely monitor patients who are dual UGT2B17 and CYP2C19 poor metabolizers due to potential increases in exposure that may increase the incidence or severity of anemia.
Transfuse patients as clinically indicated. For patients with hemoglobin (Hb) <9g/dL, withhold WELIREG until Hb≥9g/dL, then resume at reduced dose or permanently discontinue depending on the severity of anemia. For life-threatening anemia or when urgent intervention is indicated, withhold WELIREG until Hb ≥9g/dL, then resume at a reduced dose or permanently discontinue.
The use of erythropoiesis stimulating agents (ESAs) for treatment of anemia is not recommended in patients treated with WELIREG.
Hypoxia
WELIREG can cause severe hypoxia that may require discontinuation, supplemental oxygen, or hospitalization. In Study 004, hypoxia occurred in 1.6% of patients. In Study 001, a clinical trial in patients with advanced solid tumors (n=58) treated at the recommended dose, hypoxia occurred in 29% of patients; 16% were Grade 3 hypoxia.
Monitor oxygen saturation before initiation of and periodically throughout treatment. For decreased oxygen saturation with exercise (e.g., pulse oximeter <88% or PaO2 ≤55 mm Hg), consider withholding WELIREG until pulse oximetry with exercise is greater than 88%, then resume at the same or a reduced dose. For decreased oxygen saturation at rest (e.g., pulse oximeter <88% or PaO2 ≤55 mm Hg) or when urgent intervention is indicated, withhold WELIREG until resolved and resume at a reduced dose or discontinue. For life-threatening or recurrent symptomatic hypoxia, permanently discontinue WELIREG. Advise patients to report signs and symptoms of hypoxia immediately to a healthcare provider.
Embryo-Fetal Toxicity
Based on findings in animals, WELIREG can cause fetal harm when administered to a pregnant woman.
Advise pregnant women and females of reproductive potential of the potential risk to the fetus. Advise females of reproductive potential to use effective non-hormonal contraception during treatment with WELIREG and for 1 week after the last dose. WELIREG can render some hormonal contraceptives ineffective. Advise male patients with female partners of reproductive potential to use effective contraception during treatment with WELIREG and for 1 week after the last dose.
Adverse Reactions
In Study 004, serious adverse reactions occurred in 15% of patients, including anemia, hypoxia, anaphylaxis reaction, retinal detachment, and central retinal vein occlusion (1 patient each).
WELIREG was permanently discontinued due to adverse reactions in 3.3% of patients for dizziness and opioid overdose (1.6% each).
Dosage interruptions due to an adverse reaction occurred in 39% of patients. Those which required dosage interruption in >2% of patients were fatigue, decreased hemoglobin, anemia, nausea, abdominal pain, headache, and influenza-like illness.
Dose reductions due to an adverse reaction occurred in 13% of patients. The most frequently reported adverse reaction which required dose reduction was fatigue (7%).
The most common adverse reactions (≥25%) were decreased hemoglobin (93%), anemia (90%), fatigue (64%), increased creatinine (64%), headache (39%), dizziness (38%), increased glucose (34%), and nausea (31%).
In Study 001, a clinical trial in patients with advanced solid tumors (n=58) treated at the recommended dose, the following additional adverse reactions have been reported: edema, cough, musculoskeletal pain, vomiting, diarrhea, and dehydration.
Drug Interactions
Coadministration of WELIREG with inhibitors of UGT2B17 or CYP2C19 increases plasma exposure of belzutifan, which may increase the incidence and severity of adverse reactions. Monitor for anemia and hypoxia and reduce the dosage of WELIREG as recommended.
Coadministration of WELIREG with CYP3A4 substrates decreases concentrations of CYP3A4 substrates, which may reduce the efficacy of these substrates or lead to therapeutic failures. Avoid coadministration with sensitive CYP3A4 substrates. If coadministration cannot be avoided, increase the sensitive CYP3A4 substrate dosage in accordance with its Prescribing Information. Coadministration of WELIREG with hormonal contraceptives may lead to contraceptive failure or an increase in breakthrough bleeding.
Lactation
Because of the potential for serious adverse reactions in breastfed children, advise women not to breastfeed during treatment with WELIREG and for 1 week after the last dose.
Females and Males of Reproductive Potential
WELIREG can cause fetal harm when administered to a pregnant woman. Verify the pregnancy status of females of reproductive potential prior to initiating treatment with WELIREG.
Use of WELIREG may reduce the efficacy of hormonal contraceptives. Advise females of reproductive potential to use effective non-hormonal contraception during treatment with WELIREG and for 1 week after the last dose. Advise males with female partners of reproductive potential to use effective contraception during treatment with WELIREG and for 1 week after the last dose.
Based on findings in animals, WELIREG may impair fertility in males and females of reproductive potential and the reversibility of this effect is unknown.
Pediatric Use
Safety and effectiveness of WELIREG in pediatric patients under 18 years of age have not been established.