• As part of its expansion of DEP^® applications, Starpharma has developed a number of novel radiotherapeutic and radiodiagnostic candidates
• Starpharma’s first DEP^® radiotherapy candidate (DEP^® lutetium) showed highly statistically significant anticancer activity, tumour regression and 100% survival in a human prostate cancer model (DU-145)
• Radiotherapy is an increasingly important area in cancer therapy both clinically and commercially, and has recently been the subject of multiple high value transactions[1]

Melbourne, Australia; 17 June 2020: Starpharma (ASX: SPL, OTCQX: SPHRY) today announced results from its first radiotherapeutic candidate, DEP^® lutetium. DEP^® lutetium is a patented nanoparticle which incorporates the radioisotope Lutetium-177 on a DEP^® dendrimer scaffold. 

In these studies, conducted at the University of Queensland’s Centre for Advanced Imaging, the efficacy of two dose regimens of DEP^® lutetium were assessed in a human prostate cancer model (DU-145). DEP^® lutetium showed statistically significant and durable anticancer activity and was extremely well tolerated in both dose regimens.   

Both doses of DEP^® lutetium (1 x 15 MBq or 2 x 9 MBq) achieved significant anticancer activity (p<0.0001) in the DU-145 prostate cancer model. In addition a single dose (Day 1) of DEP^® lutetium (15 MBq) achieved significant anti-tumour activity with tumour regression of over 55% (Day 36) and 100% survival (>70 days).

Figure 1:  Percentage change in tumour volume over time as measured in the DU-145 human prostate cancer model.

Both dose regimens of DEP^® lutetium were extremely well tolerated and showed minimal weight loss during dosing with recovery and subsequent weight gain.

The impressive efficacy seen with both doses of DEP^® lutetium resulted in a statistically significant positive survival benefit (p<0.0001 ANOVA – Log rank (Mantell Cox) test;
Figure 2).

Figure 2:  Kaplan-Meier survival curve in the DU-145 human prostate cancer model.

Dr Jackie Fairley, Starpharma CEO, commented: “Radiotherapeutics are a rapidly growing and increasingly important area of cancer therapy, and represent an exciting extension of the DEP^® platform. The impressive efficacy and survival benefit of DEP^® lutetium illustrates the versatility of Starpharma’s DEP^® platform. DEP^® lutetium is one of several promising DEP^® radiotherapeutic candidates in development. We are delighted to be working with Professor Kristofer Thurecht at The University of Queensland’s Centre for Advanced Imaging, whose team are at the forefront of this innovative area.”

The radiopharmaceuticals area is a rapidly developing area of cancer treatment and diagnosis, and this area has recently generated several high-value deals and sales in this category are estimated to grow to $12–15 billion by 2030[2].

Study Methods

This study was a mouse xenograft using DU-145 human prostate cancer cells and was conducted by The University of Queensland’s Centre for Advanced Imaging. Balb/c mice were injected subcutaneously with DU-145 cells into the right flank of each mouse (10 mice/group).

Groups were dosed as follows:  

• Vehicle - IV vehicle on days 1, 8 and 15
• DEP^® lutetium 15 MBq – IV on day 1
• DEP^® lutetium 2 x 9 MBq - IV on days 1 and 15

Tumours were measured 2-3 times weekly using electronic callipers. Tumour volume (mm³) was calculated at each timepoint. The tumour volume data represent the mean ± standard error of the mean (SEM). Note: If error bars do not display on the graphs, they are not visible because they are shorter than the height of the symbol.

About DEP^® radiopharmaceuticals

The versatility of the DEP^® platform means it can be used with a wide range of therapies (e.g. small molecules, peptides, antibodies, antibody fragments, radioisotopes). DEP^® radiotherapeutics incorporate radioisotopes on to the DEP^® scaffold. Whilst this announcement relates to a radiotherapeutic (DEP^® lutetium), the DEP^® platform is applicable to both radiotherapeutic and radiodiagnostic applications. DEP^® radiopharmaceutical conjugates have the potential to minimise off target toxicity and enhance efficacy when used alone or in combination with other therapeutic approaches. Specific patent applications for DEP^® lutetium and further DEP^® radiotherapeutic candidates have been filed.

Download ASX Announcement: DEP® lutetium effective in human prostate cancer model (pdf file, 109kb)

[1] Acquisition of Endocyte by Novartis for US$2.1 billion and the acquisition of Sirtex by CDH Genetech for ~A$1.9 billion

[2] Nuclear medicine world market report & directory, MEDraysintell, 2016