We use the word enobosarm in terms of referring to the drug itself. In the past historically testosterone or androgens have worked very effectively against metastatic hormone receptor positive breast cancer but the problem in older drugs such as halotestin, the problem with drugs like that is that they have a lot of virilisation. So the side effects in women is somewhat unacceptable even though they’re very effective. This particular drug, enobosarm, does not have that virilisation component. It’s a selective androgen receptor modulator and so it offers a very different form of targeting the endocrine pathway in metastatic breast cancer that’s hormone receptor positive but it doesn’t have the side effects as other androgen receptor drugs.

So we look at the use of this drug as something very different than tamoxifen, for example, or the aromatase inhibitors, all of these have different mechanisms of action. So as the metastatic breast cancer becomes more resistant to other endocrine therapies we offer enobosarm as a different target, a different agent, that should overcome that resistance with very, very low toxicity. In the United States, for example, we don’t have access to androgens anymore for the treatment of breast cancer; halotestin is no longer being produced so this drug really meets a whole new market, really expands the options for endocrine therapy for this type of breast cancer.

What were the key findings within your research?

There was an older pilot trial of 22 patients highly pre-treated, more than four prior endocrine therapies as a median. We had a 35% clinical benefit rate at six months. This particular trial, which is an international trial, we were looking at two different doses of enobosarm, 9mg and 18mg. The study is not powered to compare the two doses so they’re basically two parallel phase II trials. It had a two stage design; we’re looking at a clinical benefit rate at six months of more than 30% in order to achieve efficacy and take it to the next step. Again, the study has met its accrual but there are still patients being treated. So far we have actually met our first stage and so we are now completing the second stage. The second stage includes 44 patients in each arm that have androgen receptor positive, oestrogen receptor positive metastatic breast cancer. So we’ve been very successful in terms of our clinical benefit rate and hopefully we’ll be able to take this forward into clinical practice.

What is the ultimate aim of your research?

Again the ultimate aim is to offer a different type of endocrine therapy. Right now in terms of breast cancer we have selective oestrogen receptor modulators like tamoxifen, we have aromatase inhibitors, we have selective oestrogen receptor downregulators but we don’t have anything else. So what this does is allow the selective androgen receptor modulators for hormone receptor positive breast cancer, it’s a whole new class of drugs. So the patients who have advanced disease that’s very indolent, does not require chemotherapy, can remain on a very non-toxic endocrine therapy. So it really opens up a whole new class of drugs for that patient population.

What is your take home message?

We’d like them to keep their eyes open for the further development of this drug. We hope to take it to the next level for FDA approval, for approval in clinical practice. They need to understand that the toxicity profile of this drug is extremely mild – no myalgias, tolerated very well, no virilisation, good energy level – so that they need to just keep their eyes open to see this drug put into clinical practice.