Analysts at Leerink Partners said in a Monday note that DESTIN-Breast09’s findings “could support an approval” for Enhertu in first-line HER2+ metastatic breast cancer.
AstraZeneca and Daiichi Sankyo’s antibody-drug conjugate Enhertu cleared the Phase III DESTINY-Breast09 study, improving progression-free survival when used as a first-line therapy in patients with HER2-positive breast cancer, according to a readout on Monday.
In a note to investors, analysts at Leerink Partners said these new findings “could lead to a change in the treatment paradigm in HER2+ metastatic breast cancer,” adding that doctors seem “enthusiastic about Enhertu entering the frontline.” Still, safety could be a “key factor” in determining the penetration and clinical value of Enhertu in this setting, the analysts said.
DESTINY-Breast09 tested Enhertu either alone or with Roche’s Perjeta, a HER2 receptor blocker, as a frontline option in patients with metastatic breast cancer. As a control, the trial pitted this combo against a regimen called THP—consisting of a taxane chemotherapy (docetaxel or paclitaxel), Roche’s monoclonal antibodies Herceptin and Perjeta—currently the standard of care in this indication.
Without providing specific data, AstraZeneca and Daiichi Sankyo noted that the Enhertu combo elicited a “highly statistically significant and clinically meaningful improvement” in progression-free survival (PFS), DESTINY-Breast09’s primary endpoint. This PFS benefit was present across various patient subgroups.
Overall survival, while not mature at the time of the readout, demonstrated a trend in favor of the Enhertu regimen, as per Monday’s release.
Details regarding safety were sparse. The partners only revealed that side effects in the Enhertu combo arm were “consistent” with what is known for the individual agents. AstraZeneca and Daiichi Sankyo will present detailed findings from DESTINY-Breast09 at an upcoming medical congress and will present Monday’s data to health authorities.
“This dataset could support an approval in 1L HER2+ metastatic breast cancer,” as per the Leerink note. Analysts added, however, that investors will be on the lookout for key tolerability data, including grade 3 complications, interstitial lung disease and discontinuation rates. “These data could factor into physician and patient treatment decisions,” they noted.
It’s been a good year so far for Enhertu, which in January won the FDA’s nod for a breast cancer expansion. The regulator approved the use of the drug in patients with metastatic or unresectable breast cancer with ultralow expression levels of the HER2 marker. Earlier this month, the European Union also gave the go-ahead for Enhertu in HR-positive, HER2-low or HER2-ultralow metastatic breast cancer.
Last month, AstraZeneca and Daiichi Sankyo beefed up their case for Enhertu’s expansion into gastric cancer with a Phase III readout, touting significant and meaningful overall survival benefits when used as a second-line therapy.
