Castration-resistant prostate cancer (CRPC)

CRPC is an incurable stage of prostate cancer, in which approx. 90% of patients develop metastases, mainly in the skeleton. Patients can experience acute pain due to fractures, compression of the spine and other skeletal symptoms. Skeletal pain is generally the most common form of cancer-related pain, and can be severe and cause invalidity in the majority of patients, with a resulting negative effect on quality of life and mobility. Experienced clinicians describe CRPC as a skeletal disease. Over time, the existing treatment available is ineffective and the patient will die of his disease. Mean survival time for CRPC is around 1 – 2 years1.

Essentially all patients dying from prostate cancer today have CRPC. There are only a few medications registered for the treatment of CRPC at this time: docetaxel (Taxotere) and cabazitaxel (Jevtana), both of which are cytostatics, plus abirateron (Zytiga), enzalutamid (Xtandi) and Radium-223 (Xofigo). Abirateron and enzalutamid are hormonally active (impair/block), whilst Radium-223 binds to the area of the skeleton where subsidiary tumours (metastases) are located and releases a local radioactive effect there. These five drugs have been shown to impair the tumour disease in most patients, and extend survival by around 2.5 – 5 months.

All have side effects to some degree, and individual patient status will determine the therapy that can be used. All treatment of CRPC patients is intended to be disease impairing and palliative, as it can only extend patient life at best. Every single one of these medications has a relatively short efficacy time, as the disease becomes resistant to the drug after a short period, which means it has to be replaced by another (figure 7). Providing a new medication comes onto the market, CRPC could – best case – become a chronic disease. There are no curative medications currently in sight.

Figure 7: y axis = PSA µg/L, x axis = time. The figure shows a typical CRPC patient and disease development. The Y axis describes cancer activity, PSA, in a patient when medication (blue arrow) reduces cancer activity, but when the patient develops resistance after a while to the medication, PSA values rise again. The patient is therefore given a new medication and the cycle repeats until there are no alternative medications.

Figure 7: y axis = PSA µg/L, x axis = time. The figure shows a typical CRPC patient and disease development. The Y axis describes cancer activity, PSA, in a patient when medication (blue arrow) reduces cancer activity, but when the patient develops resistance after a while to the medication, PSA values rise again. The patient is therefore given a new medication and the cycle repeats until there are no alternative medications.

Against this background, DexTech prefers to develop a complementary rather than competitive medication. The CRPC market is expected to continue to grow due to an increasingly ageing population. There is high demand for a new drug able to extend live with relative maintenance of quality of life. OsteoDex has the potential to become another medication able to influence the prognosis, i.e. survival time with acceptable quality of life for patients with CRPC.

1 Kirby, M. , Characterising the castration-resistant prostate cancer population: a systematic review, The International Journal of Clinical Practice.