How Does Piqray Work For HER2-Negative, HR+ Metastatic Breast Cancer?

As a “first-in-class drug,” Piqray is the very first PI3K inhibitor to enter the market for breast cancer treatment. A PI3K inhibitor is a drug that works by blocking the PI3K (phosphoinositide 3-kinase) enzyme, which has an essential function in allowing cellsincluding cancer cellsto grow.

Who Can Benefit From the Drug?

Piqray was specifically approved for use in combination with the endocrine therapy fulvestrant. Together, the drugs will treat patients with hormone receptor (HR)-positive, HER2-negative metastatic breast cancers that have progressed after treatment with fulvestrant alone or other endocrine-based regimens.

The approval also stipulates that the patients must be post-menopausal, and thatand this is the most important aspect of this approvaltheir breast cancer tumor must express a mutation on the PIK3CA gene.

“Piqray is the first FDA-approved drug that targets one of the most commonly mutated genes in breast cancer,” Dr. Hatem Soliman, medical breast cancer oncologist and Director of the Clinical Trials Office at the Moffitt Cancer Center, told SurvivorNet. Dr. Soliman added that it is estimated that about 30 to 40 percent of metastatic breast cancer tumors may harbor one of these PIK3CA mutations, which play an active role in driving tumor growth and making cancers resistant to various therapies.

Dr. Erica Mayer explains how metastatic hormone receptor positive breast cancer is typically treated.

How Do I Know if I Have a PIK3CA Mutation?

Because the presence of a PIK3CA gene mutation is essential to determining whether a patient is eligible for treatment with Piqray, the FDA also approved a new genetic test specifically for this purpose. The genetic test, which is called therascreen PIK3CA RGQ PCR Kit, can identify 11 different mutations on the PIK3CA gene.

How Effective is Piqray?

“The benefit is definitely significant,” Dr. Abraham said of Piqray. The new drugwhich is taken as an oral tabletwas FDA-approved after promising results surfaced from a clinical trial called SOLAR-1, during which 572 participants received fulvestrant in combination with either Piqray or a placebo. After monitoring the patients on the clinical trial for three years, the researchers found that the patients who took the Piqray in combination with their fulvestrant had a median progression-free survival of 11 months, versus 5.7 months for those patients who received a placebo.

“Based on data from the SOLAR-1 trial, it appears that Piqray, when added to antiestrogen therapy, almost doubled the progression-free survival of women with metastatic breast cancers harboring mutations in the PIK3CA gene,” Dr. Soliman said. “This development is considered a significant milestone in our efforts to improve outcomes for our metastatic breast cancer patients using personalized medicine and targeted drugs.”

My Advanced Breast Cancer Isn’t Eligible for Treatment With Piqray Now What?

There are other options. Piqray may be a new name on the block for targeted breast cancer treatment, but it's not alone. Piqray joins other targeted metastatic breast cancer treatments on the market, including CDK 4/6 Inhibitors, aromatase inhibitors, and mTOR inhibitors.

And as researchers continue to identify specific genetic characteristics of breast cancer tumors, new drug approvals will likely go hand-in-hand. Because the field is always advancing, it's important for all patients diagnosed with breast cancerregardless of the type or stageto undergo genetic testing.

Dr. Elizabeth Comen, medical oncologist at Memorial Sloan Kettering Cancer Center, recently explained the growing importance of genetic testing after a breast cancer diagnosis to SurvivorNet.

"What we can now do in medical science for some patients is what’s called genetic sequencing, meaning we take a piece of the tumor, and we look at all the genes that help make up the blueprint of that tumor and try to figure out, what are the mutations that evolved in that cancer, specifically to allow it to grow?"

Dr. Comen went on to explain why that sequencing is critical: "The reason why that’s important is it might make certain clinical trials appropriate for a patient," she said. "A new medicine might target that mutation, or there may already be existing medications that target that mutation."

For patients with mutations of the BRCA gene, for instance, a whole class of drugs called PARP inhibitors (olaparib and talazoparib) may be an option, and for patients with HER2-positive tumors, lifesaving treatments such as trastuzumab (Herceptin) may be an option. Many of these targeted treatments may be used in combination with more traditional treatment methods, such as chemotherapy, surgery, or radiation.

And even if your specific cancer doesn’t turn out to be eligible for targeted treatments already on the market, as Dr. Comen suggested, genetic sequencing could reveal that you're eligible to participate in a clinical trial for a new drug.

"The science is evolving at a rapid pace, where increasingly, we are finding new mutations that may make people eligible for clinical trials," she said. "It’s important that patients talk to their doctor about whether they have the type of cancer for which, if a mutation was found, there might be a clinical trial available that would match that mutation to a given targeted agent."

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