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Welcome back to the D.I.S.C.O., FDA’s Drug Information Soundcast in Clinical Oncology, Burst Edition, brought to you by FDA’s Division of Drug Information in partnership with FDA’s Oncology Center of Excellence. Today we’ll provide a quick update on two recent FDA cancer drug approvals.

On January 27, 2023, the FDA granted accelerated approval to pirtobrutinib (brand name Jaypirca) for relapsed or refractory mantle cell lymphoma after at least two lines of systemic therapy, including a BTK inhibitor.

Efficacy was evaluated in BRUIN, an open-label, multicenter, single-arm trial of pirtobrutinib monotherapy that included 120 patients with mantle cell lymphoma previously treated with a BTK inhibitor. Patients had a median of 3 prior lines of therapy, with 93% having 2 or more prior lines. The most common prior BTK inhibitors received were ibrutinib, acalabrutinib, and zanubrutinib; 83% had discontinued their last BTK inhibitor due to refractory or progressive disease. Pirtobrutinib was administered orally at 200 mg once daily and was continued until disease progression or unacceptable toxicity.

The main efficacy measures were overall response rate and duration of response, as assessed by an independent review committee using Lugano criteria. The overall response rate was 50% with a complete response rate of 13%. The estimated median duration of response was 8.3 months, and the estimated duration of response rate at 6 months was 65.3%.

The most common adverse reactions occurring in more than 15% of patients with mantle cell lymphoma were fatigue, musculoskeletal pain, diarrhea, edema, dyspnea, pneumonia, and bruising. Grade 3 or 4 laboratory abnormalities in greater than 10% of patients were decreased neutrophil counts, lymphocyte counts, and platelet counts. The prescribing information includes warnings and precautions for infections, hemorrhage, cytopenias, atrial fibrillation and flutter, and second primary malignancies.

This review used the Assessment Aid, a voluntary submission from the applicant to facilitate the FDA’s assessment.

On January 27, 2023, the FDA approved elacestrant (brand name Orserdu) for postmenopausal women or adult men with ER-positive, HER2-negative, ESR1-mutated advanced or metastatic breast cancer with disease progression following at least one line of endocrine therapy.

FDA also approved the Guardant360 CDx assay as a companion diagnostic device to identify patients with breast cancer for treatment with elacestrant.

Efficacy was evaluated in EMERALD, a randomized, open-label, active-controlled, multicenter trial that enrolled 478 postmenopausal women and men with ER-positive, HER2-negative advanced or metastatic breast cancer of which 228 patients had ESR1 mutations. Patients were required to have disease progression on one or two prior lines of endocrine therapy, including one line containing a CDK4/6 inhibitor. Eligible patients could have received up to one prior line of chemotherapy in the advanced or metastatic setting. Patients were randomized (1:1) to receive elacestrant 345 mg orally once daily or investigator’s choice of endocrine therapy, which included fulvestrant or an aromatase inhibitor. Randomization was stratified by ESR1 mutation status, prior treatment with fulvestrant, and visceral metastasis. ESR1 mutational status was determined by blood circulating tumor deoxyribonucleic acid using the Guardant360 CDx assay and was limited to ESR1 missense mutations in the ligand binding domain.

The major efficacy outcome measure was progression-free survival, assessed by a blinded imaging review committee. A statistically significant difference in progression-free survival was observed in the intention to treat population and in the subgroup of patients with ESR1 mutations.

In the 228 patients with ESR1 mutations, median progression-free survival PFS was 3.8 months in the elacestrant arm and 1.9 months in the fulvestrant or aromatase inhibitor arm.

An exploratory analysis of progression-free survival in the 250 patients without ESR1 mutations showed a hazard ratio of 0.86 indicating that the improvement in the intention to treat population was primarily attributed to the results seen in the ESR1 mutated population.

The most common adverse events occurring in more than 10% of patients, including laboratory abnormalities, were musculoskeletal pain, nausea, increased cholesterol, increased AST, increased triglycerides, fatigue, decreased hemoglobin, vomiting, increased ALT, decreased sodium, increased creatinine, decreased appetite, diarrhea, headache, constipation, abdominal pain, hot flush, and dyspepsia.

This review used the Assessment Aid, a voluntary submission from the applicant to facilitate the FDA’s assessment.

Full prescribing information for these approvals can be found on the web at www.fda.gov/drugsatFDA.

Health care professionals should report serious adverse events to FDA’s MedWatch Reporting Program at www.fda.gov/medwatch.

Follow the Division of Drug Information on Twitter @FDA_Drug_Info and the Oncology Center of Excellence @FDAOncology. Send your feedback via email to FDAOncology@fda.hhs.gov. Thanks for tuning in to the D.I.S.C.O. Burst Edition.