*

Trodelvy/Keytruda patients had 11.2 months

progression-free

survival vs 7.8 months for chemotherapy/Keytruda

*

ASCO says Trodelvy/Keytruda likely to become standard of

care

*

Patients still being followed to see if combination

extends

survival

By Deena Beasley

May 31 (Reuters) - Gilead Sciences' ( GILD ) Trodelvy in

combination with Merck's ( MRK ) blockbuster immunotherapy

Keytruda lowered the risk of an aggressive type of breast cancer

worsening by 35% when used as an initial treatment, according to

results of a large trial presented on Saturday.

The data is likely to change how patients are treated

following a diagnosis for advanced triple-negative breast

cancer, one expert said.

After a median follow-up of 14 months, patients treated with

Trodelvy, a so-called antibody-drug conjugate, and Keytruda went

11.2 months without their cancer progressing, a measure known as

progress-free survival. That compared with PFS of 7.8 months for

those given the standard treatment of chemotherapy and Keytruda,

researchers said.

Patients given the Trodelvy/Keytruda combination responded

to the treatment for a median of 16.5 months, compared with 9.2

months for the chemo group, according to full results of the

study presented at the American Society of Clinical Oncology

scientific meeting in Chicago. The researchers said patients are

still being followed to see if the regimen has an impact on

overall survival.

Gilead previously said the Phase 3 study in 443 patients

with advanced triple-negative breast cancer whose tumors express

PD-L1 - the protein targeted by drugs like Keytruda - had met

its goal.

The findings suggest that the combination of Trodelvy and

Keytruda "will likely become a new front-line standard of care

in this setting," Dr. Jane Lowe Meisel, co-director of breast

oncology at Emory University School of Medicine and a designated

ASCO expert said in a statement.

ASCO estimates that about 10% of breast cancers in the

United States are triple-negative. That tends to be more

difficult to treat than hormone-sensitive subtypes, because it

does not have the common biomarkers used to guide treatment, the

tumors are often larger, and the recurrence rate is high.

The medical group said that about 40% of triple-negative

breast cancers are also PD-L1 positive, making them candidates

for Keytruda.

Antibody-drug conjugates like Trodelvy are designed to

deliver an anti-cancer drug more precisely to malignant cells,

causing less damage to healthy cells than chemotherapy.

Serious side effects for Trodelvy included neutropenia, a

condition caused by cancer treatments that lower levels of

infection-fighting white blood cells, reported in 43% of

patients, and diarrhea in 10%. In the chemotherapy group, the

incidence of neutropenia was 45%, while 16% of patients had

anemia and 14% had low blood platelet counts.

Trodelvy is already approved for patients with advanced

triple-negative breast cancer who had two or more prior

therapies, and for previously treated hormone-receptor-positive,

HER2-negative metastatic breast cancer.

Gilead is conducting several other Trodelvy studies,

including a trial of the drug as an initial treatment for

triple-negative breast cancer patients who do not express PD-L1.