Researchers are recruiting volunteers for a clinical trial they hope will improve survival rates for an aggressive form of breast cancer that affects about 1,500 women each year in New South Wales.
NSW researchers are calling for volunteers for a new clinical trial to test a new strategy in cancer treatment: using a new therapy to target a ‘defense switch’ on cancer cells that alerts cancer to the threat of chemotherapy.
The trial aims to improve survival rates for patients with triple-negative breast cancer, a treatment-resistant form of cancer that can quickly adapt to chemotherapy.
It will be led by Associate Professor Christine Chaffer and Dr. Beatriz San Juan from the Garvan Institute of Medical Research, and Senior Staff Specialist in medical oncology Dr. Rachel Dear of St Vincent’s Hospital Sydney. The trial will be conducted at The Kinghorn Cancer Centre in Darlinghurst.
Associate Professor Christine Chaffer. Image credit: Garvan Institute
The research leading to the trial has been supported by the NELUNE Foundation, which awarded Associate Professor Chaffer the Rebecca Wilson Fellowship in Cancer Research in 2017, enabling her to bring her research back to Sydney from the USA. The Fellowship is a lasting legacy to sports journalist the late Rebecca Wilson.
“Triple-negative breast cancer is an aggressive disease with a greater likelihood of spreading around the body and recurring within five years than other breast cancers.
“In preclinical studies, we found that an experimental drug, seviteronel, combined with chemotherapy, could be twice as effective in reducing the size of tumors than chemotherapy alone,” says Associate Professor Chaffer.
Androgen hormones tell triple-negative breast cancer to adapt against chemotherapy and to behave aggressively. Seviteronel works by blocking these warning signals and potentially makes other treatments more effective.
Dr. Dear says, “this is an exciting opportunity to test a new treatment option for metastatic triple-negative breast cancer, for which there is currently a gap in effective drug treatments.”
Seviteronel is not currently approved for clinical use. If this trial is successful, it will be followed by a larger safety study within a year.
A new approach for triple-negative breast cancer
About 10-15% of breast cancer cases are diagnosed as triple-negative breast cancer, which means the cancer cells lack all three receptors that doctors can target with cancer-treating medications. As there are currently no effective targeted therapies, triple-negative breast cancers have a poorer prognosis than other forms of breast cancer.
Research from Associate Professor Chaffer’s team revealed that triple-negative cancer cells ‘switch’ their cell state in response to chemotherapy, which not only makes the cancer cells more aggressive but also allows them to evade treatment.
“We found that chemotherapy triggers a cell change in cancer cells that enables them to build a defense against the chemotherapy. This means that a different type of cancer cell emerges after treatment, which has become resistant to the chemotherapy and is a major cause of cancer relapse,” Associate Professor Chaffer explains.
“We aim to stop this cancer resistance strategy to improve the effectiveness of chemotherapy for triple-negative breast tumors”.
Dr Beatriz Perez San Juan, the post-doctoral researcher in Associate Professor Chaffer’s lab who led the preclinical study, discovered that activation of androgen receptors in breast cancer cells triggers the cell state switching. Androgens are commonly thought of as male sex hormones but are also found at lower levels in women.
In preclinical models of triple-negative breast cancer, the researchers administered chemotherapy together with seviteronel, an experimental treatment that blocks androgen production. The combination approach caused a 70% to 100% greater reduction in tumor size compared to chemotherapy alone. This strategy prevented the emergence of chemotherapy-resistant cells and reduced the spread of cancer around the body.
Androgen receptor hormone. Image credit: Dr Kate Patterson
Repurposing an experimental treatment
Seviteronel was originally developed as a standalone therapy for breast and prostate cancers that carry the androgen receptor and was proven safe for patients in Phase II clinical trials.
“Our research has revealed that seviteronel may be far more beneficial as an adjunct therapy. We found that androgen inhibition blocks cancer cell state switching, ‘locking’ cancer cells in a chemotherapy-sensitive state. This is why chemotherapy plus seviteronel treatment was more effective than chemotherapy alone at targeting cancer in our preclinical studies,” says Dr. Perez San Juan.
Seviteronel (light blue) binding to androgren receptor (purple) to block the androgen hormone (red). Image credit: Dr Kate Patterson
“We hope that this new combination treatment approach will drastically reduce drug resistance to improve the effectiveness of standard-of-care chemotherapy and, ultimately, improve patient outcomes.”
Source: Garvan Institute