New SERM Shows Promise in Advanced Breast Cancer

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https://www.medpagetoday.com/hematologyoncology/breastcancer/68893

"New SERM Shows Promise in Advanced Breast Cancer

Phase I study demonstrated clinical benefit, unaffected by CYP2D6 metabolism"

"Action points:

In women with estrogen receptor-positive, hormone-refractory metastatic breast cancer, oral Z-endoxifen hydrochloride, the potent metabolite of tamoxifen, provided substantial drug exposure regardless of CYP2D6 genotype, acceptable toxicity, and promising antitumor activity.

Note that the study was unable to determine the maximum-tolerated dose of oral endoxifen, and dose escalation was discontinued at 160 mg per day and endoxifen concentrations >1,900 ng/mL."

"In women with estrogen receptor-positive, hormone-refractory metastatic breast cancer, oral Z-endoxifen hydrochloride, the potent metabolite of tamoxifen, provided substantial drug exposure regardless of CYP2D6 genotype, acceptable toxicity, and promising antitumor activity, researchers reported.

Results from a phase I study in 38 patients with metastatic breast cancer demonstrated a clinical benefit rate (stable disease ≥ 6 months) of 26.3%. including a partial response by RECIST criteria in three patients who experienced progression during prior tamoxifen therapy, according to Matthew P. Goetz, MD, of the Mayo Clinic in Rochester, Minnesota, and colleagues.

Clinical benefit was also seen in seven patients who had no prior tamoxifen treatment or who didn't experience progression with adjuvant tamoxifen. The median progression-free survival (PFS) time was 110 days, with a 1-year PFS rate of 15%, they wrote online in the Journal of Clinical Oncology.

The study was unable to determine the maximum-tolerated dose of oral endoxifen"