Drug in breast cancer trials shows potential for treating blood cancers

Two new studies led by researchers at Washington University School of Medicine in St. Louis have identified a possible way to block the progression of several forms of blood cancer using a drug already in clinical trials against breast cancer.

The studies – both conducted in patient samples and animal models – found that inhibiting a protein called RSK1 reduces inflammation and stops the progression of blood cancers called myeloproliferative neoplasms (MPNs) as well as an aggressive form of acute myeloid leukemia (AML). With the RSK1 inhibitor already in clinical testing, the path to expanded use as a treatment for blood cancers likely is accelerated.

In the Nature Communications study, inhibiting RSK1 helped reverse the progression of MPNs in mice, reducing fibrosis, or scar formation, in the bone marrow. Inhibiting RSK1 eliminated up to 96% of cancer in mice after four weeks. It also showed evidence of preventing the chronic disease from transforming into secondary AML.

In the Blood Cancer Journal study, blocking this protein treats a specific form of AML called FLT3-ITD AML that develops directly – without an MPN developing first. This type of AML can be treated with established drugs called FLT3 inhibitors, but the cancer often develops resistance to this treatment over time. Because the RSK1 inhibitor blocks a different pathway, Oh and his co-authors suggested, it could help address this resistance.

The specific RSK1 inhibitor used in both studies, called PMD-026, is given as a pill and is currently in clinical trials as a treatment for breast cancer. Those ongoing studies seek to determine efficacy, and early testing showed trial subjects with metastatic breast cancer have tolerated the drug well with low-grade side effects.

Gabrielle’s Angel Foundation is listed in both studies for our support of Grant Challen, PhD at Washington University in St. Louis, who we funded with a Medical Research Award in 2016 and The Mark Foundation for Cancer Research Collaborative Grant in 2023. We are proud to have played a small role in this major research breakthrough and look forward to seeing the next steps for this important project! 

Read the full article here.