Melbourne, Australia; Starpharma Holdings (ASX: SPL, OTCQX: SPHRY) today released animal data which demonstrated that its dendrimer-docetaxel formulation applying Starpharma’s dendrimer technology to the leading chemotherapy drug docetaxel was significantly more efficacious than docetaxel (Taxotere^®) in a breast cancer model.

Docetaxel is a leading chemotherapy drug used to treat a wide range of solid tumours including breast, lung and prostate.  It is marketed by Sanofi Aventis as Taxotere^® and generated sales in excess of US$3 billion in 2010.

Starpharma conducted the latest study, a breast cancer xenograft in mice, as part of its drug delivery program for docetaxel - having already demonstrated a marked improvement in the water solubility of docetaxel with its dendrimer formulation. This study was designed to assess the efficacy of Starpharma’s dendrimer-docetaxel formulations in treating cancer.

The results of this study show Starpharma’s dendrimer-docetaxel formulation demonstrated a significant enhancement of anticancer effect when compared to docetaxel/Taxotere^® alone. Furthermore, 60% of animals treated with Starpharma’s preferred dendrimer-docetaxel formulation had no evidence of tumours at 94 days - whereas 100% of the docetaxel treated mice showed significant tumour re-growth or recurrence at the same time point.

Starpharma Chief Executive Officer, Dr Jackie Fairley said: “These initial results of our dendrimer-docetaxel program are extremely encouraging. To have a high proportion of animals with no evidence of tumours and a significant improvement in efficacy versus docetaxel is a great result. These findings together with the ability of Starpharma’s dendrimers to markedly improve water solubility represent a compelling product proposition.

In the xenograft study mice were implanted with breast cancer cells which were allowed to grow to a predetermined tumour size (100 mm³) and then 10 mice per group were dosed with either dendrimer-docetaxel, docetaxel alone, or saline on days 1, 8 and 15.  Tumour volume was then assessed by manual measurement and the mean volume is plotted against time (days) in Figure 1.   

Figure 1: Mouse Xenograft – Breast Carcinoma (MDA-MB-231)

Mean tumour volume (mm3 ) v’s time (days); n=10 per group at commencement of study)

For both actives the tumour volume decreased following dosing.  However, by day 60 all tumours in the docetaxel group began to regrow. In contrast, in the dendrimer-docetaxel group there was no evidence of tumour regrowth up to day 94 (which is well beyond the typical duration of xenograft studies). Based on this and other data for dendrimer constructs it is believed that the improved efficacy of the dendrimer-docetaxel formulation is most likely due to a longer circulating half-life, the extended release of docetaxel from the dendrimer and the targeting of the dendrimer construct to tumour tissue.

The improvements in efficacy seen in this experiment are in addition to the benefit of improved water solubility with docetaxel announced in June 2011 which would also potentially allow the removal of formulation components in existing drugs thought to cause severe allergic reactions and fluid retention in some patients.

Starpharma’s docetaxel program will continue to run in parallel with its partnered drug-delivery programs which include a growing list of major pharmaceutical companies including GSK and Lilly.  Further pre-clinical studies are now planned for the dendrimer-docetaxel formulation prior to clinical studies. Detailed results of this study are expected to be presented at future scientific conferences.

Download ASX Announcement: Starpharma's dendrimers improve efficacy of docetaxel in animals (pdf file, 189kb)