Novel compound holds potential for next-generation prostate cancer treatment

In the search for new ways to attack recurrent prostate cancer, researchers at Duke Health report that a novel compound appears to have a unique way of blocking testosterone from fueling the tumors in mice.

The potential foundation for a next-generation therapy, called tetraaryl cyclobutane, or CB, is being studied as an option for prostate tumors that have grown resistant to current anti-androgen drugs, notably enzalutamide. (see below structure)

"Prostate cancer is the most prevalent form of cancer in men, and the principal driver of tumor growth is the androgen receptor," said John D. Norris, Ph.D., associate research professor in the Department of Pharmacology & Cancer Biology at Duke and senior author of a study published online Aug. 8 in the journal Nature Chemical Biology.

"Suppression of androgen receptor function by anti-endocrine therapies is initially effective, but most tumors develop resistance, resulting in a more aggressive cancer," Norris said. "Our research has been focused on finding a new approach to suppressing androgen receptor activity, because even in situations where tumors are resistant to current therapies, the androgen receptor remains a viable target."

  

Norris and colleagues focused on a group of CB compounds developed in collaboration with scientists at the University of Illinois at Urbana-Champaign. The compounds act as competitive inhibitors of androgen receptors, but are structurally different from current anti-androgens such as enzalutamide.

One of the CB compounds, in particular, inhibits mutant forms of the androgen receptors that promote resistance to enzalutamide. It functions by preventing the androgen receptor from entering the nucleus of the cell where it can promote tumor growth.

"It's encouraging that this compound has a different mechanism of action when compared to current therapies, which gives it a good chance of having efficacy in resistant disease," Norris said. "We have shown in animal models that the compound has activity against prostate tumors where enzalutamide fails."

Norris said additional studies are underway in additional animal models and in tests with other forms of cancer, including breast cancer.

Ref: http://www.nature.com/nchembio/journal/vaop/ncurrent/full/nchembio.2131.html#compounds

Novel compound holds potential for next-generation prostate cancer treatment

Enzalutamide: Indication of major added benefit for over 75-year-olds

In continuation of my update on enzalutamide

According to the findings, in comparison with watchful waiting the drug can prolong overall survival and delay the occurrence of disease complications. In men aged 75 years or older, IQWiG sees an indication of a major added benefit. There is also an indication of an added benefit in younger men; however, the extent is rated as "considerable."

Approval study terminated prematurely

The assessment was based on a randomized controlled trial (PREVAIL), which was the approval study for the indication described above. In this study, patients received either enzalutamide or a placebo, while the hormone-blocking medication was continued in all patients. In each study arm, treatment was continued until either the disease worsened (progression) or safety concerns arose, for example, because toxicity was too high.

As the interim analysis planned for the outcome "overall survival" had already shown good efficacy of enzalutamide, this was considered as the final Analysis.

Survival advantage depends on age

The difference in overall survival is statistically significant between the two study arms. However, as the further analysis of the data shows, this advantage is age dependent. It is greater in older men (75 years or more) than in younger ones. In each case, the IQWiG researchers derive an indication of an added benefit from these results, albeit with a different extent (major or minor).

Bone-related complications occur later

The study data also showed relevant group differences in favour of enzalutamide for other outcomes. For instance, bone-related complications occurred later in patients receiving enzalutamide than in those receiving placebo. IQWiG sees an indication of an added benefit here.

In addition, it took longer until opiates were used, that is, severe pain occurred later in patients receiving enzalutamide. This also applies to the occurrence of side effects (severe and serious adverse events) and the discontinuation of treatment due to side effects. Health-related quality of life also deteriorated later.

Enzalutamide: Indication of major added benefit for over 75-year-olds