FDA Approves Oral Tx for Metastatic Breast Cancer – Orserdu

We missed one!

The FDA recently (back on January 27th) approved a new ORAL therapy, Orserdu (elacestrant) from Stemline Therapeutics, Inc., indicated 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. 

Orserdu is the first oral Selective Estrogen Receptor Degrader (SERD) that has shown improved efficacy over standard of care (SOC) treatments in patients with advanced breast cancer. 

Attempting to pin down prevalence numbers, given the variables listed in the indication, is akin to picking the next winning Powerball number. Published studies have not yet been able to determine the exact prevalence rate of ESR1 mutations but set the outer boundaries between 11-55%. The prevalence of ESR1 mutations in patients depends on prior duration and setting of endocrine therapy. Approximately 20–40% of patients who have received aromatase inhibition (AI) for MBC have ESR1 mutations, with prevalence varying by sites of metastatic disease. These mutations rarely exist (0–3%) in primary tumors but are relatively common in metastatic endocrine therapy-resistant breast cancer lesions, with a wide-ranging prevalence of 6–55%.

Orserdu hit the market at a discounted price of $24,000 for a month’s supply (345mg) and $7500 for thirty 86 mg tablets.

Stemline announced that Orserdu will only be available through limited distribution. 

CLICK HERE to access prescribing information


FDA approves elacestrant for ER-positive, HER2-negative, ESR1-mutated advanced or metastatic breast cancer

On January 27, 2023, the Food and Drug Administration (FDA) approved elacestrant (Orserdu, Stemline Therapeutics, Inc.) 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 (NCT03778931), 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 (n=239) or investigator’s choice of endocrine therapy (n=239), which included fulvestrant (n=166) or an aromatase inhibitor (n=73). Randomization was stratified by ESR1 mutation status (detected vs. not detected), prior treatment with fulvestrant (yes vs. no), and visceral metastasis (yes vs. no). ESR1 mutational status was determined by blood circulating tumor deoxyribonucleic acid (ctDNA) 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 (PFS), assessed by a blinded imaging review committee. A statistically significant difference in PFS was observed in the intention to treat (ITT) population and in the subgroup of patients with ESR1 mutations.

In the 228 (48%) patients with ESR1 mutations, median PFS was 3.8 months (95% CI: 2.2, 7.3) in the elacestrant arm and 1.9 months (95% CI: 1.9, 2.1) in the fulvestrant or aromatase inhibitor arm (hazard ratio [HR] of 0.55 [95% CI: 0.39, 0.77], 2-sided p-value=0.0005).

An exploratory analysis of PFS in the 250 (52%) patients without ESR1 mutations showed a HR 0.86 (95% CI: 0.63, 1.19) indicating that the improvement in the ITT population was primarily attributed to the results seen in the ESR1 mutated population.

The most common adverse events (≥10%), 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.

The recommended elacestrant dose is 345 mg taken orally with food once daily until disease progression or unacceptable toxicity.

This application was granted priority review and fast track designation.


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