Many new treatments for metastatic breast cancer are being studied and treatment is improving. Most are drug therapies. Findings from clinical trials of these treatments will determine whether they become part of standard care for metastatic breast cancer. Some may also prove effective for treating early-stage breast cancer.

Selective estrogen receptor degraders, or SERDs, are a type of hormone therapy. These anti-estrogen drugs bind to the estrogen receptor in a tumor cell. They cause the receptor to be broken down by the cell. New SERDs are under study for the treatment of metastatic breast cancer, including several drugs that are pills.

Selective androgen receptor agonists are drugs that slow the growth of breast cancers that have androgen receptors.

CDK7 is an enzyme important in cell growth. CDK7 inhibitors are drugs designed to interrupt the growth of cancer cells. CDK7 inhibitors in combination with hormone therapy are under study for the treatment of metastatic breast cancer.

PI3 kinase is an enzyme important in cell growth. The PIK3CA gene helps control PI3 kinase enzyme activity. Some breast cancers have a mutation in the PIK3CA gene. This gene mutation is in the genes of breast cancer, not the person. It can affect PI3 kinase and cause the tumor to grow.

PI3 kinase inhibitors are drugs designed to interrupt PI3 kinase signals and stop the growth of cancer cells.

The PI3 kinase inhibitor alpelisib, or Piqray, is FDA-approved to treat some metastatic breast cancers. Other PI3 kinase inhibitors and other drugs that treat metastatic breast cancers with a PIK3CA tumor gene mutation are under study.

Immunotherapy drugs help the body’s immune system attack cancer cells. The immunotherapy drug pembrolizumab, or Keytruda, is FDA-approved for the treatment of some metastatic triple negative breast cancers. Other immunotherapy drugs are under study for the treatment of metastatic breast cancer.

Antibody-drug conjugates are a combination of an antibody therapy and a chemotherapy drug. Combining these into one drug allows the targeted delivery of the chemotherapy to specific cancer cells. Some breast cancers express a protein called Trop-2. As mentioned before, triple negative breast cancers tend to express Trop-2.

Sacituzumab govitecan, or Trodelvy, is an FDA-approved Trop-2 antibody-drug conjugate used to treat metastatic triple negative breast cancers. It’s under study for the treatment of hormone receptor-positive, HER2-negative metastatic breast cancers.

Other Trop-2 antibody-drug conjugates are also under study for the treatment of metastatic breast cancer.

PARP inhibitors are used to treat metastatic breast cancer in people who have a BRCA1 or BRCA2 inherited gene mutation. The PARP inhibitors olaparib, or Lynparza, and talazoparib, also known as Talzenna, are FDA-approved for the treatment of HER2- negative metastatic breast cancer in people who have a BRCA1 or BRCA2 inherited gene mutation.

Study findings suggest women with metastatic breast cancer who have a PALB2 inherited gene mutation may also benefit from treatment with olaparib.

Other PARP inhibitors are under study for the treatment of metastatic breast cancer.

G-quadruplex stabilizer drugs are under study for the treatment of metastatic breast cancer in people who have a BRCA1, BRCA2 or PALB2 inherited gene mutation.

Tumors often develop resistance, or stop responding, to drugs used to treat metastatic breast cancer. New ways to monitor response to treatment are under study.

Circulating tumor cell levels and circulating tumor DNA (sometimes called liquid biopsies) are under study for use in monitoring metastatic breast cancer and predicting treatment response and survival. They are not used today to guide treatment because they haven’t been shown to offer benefit. However, they are under study.

Susan G. Komen has partnered with BreastCancerTrials.org and several other organizations to provide Metastatic Trial Search, the first-ever clinical trial search engine designed specifically for people with metastatic breast cancer. You can find it in the Metastatic Breast Cancer section of komen.org.

If you or a loved one need information or resources about clinical trials, call the Komen Breast Care Helpline at 1-877 GO KOMEN (1-877- 465- 6636) or email clinicaltrialinfo@komen.org.