A Proof of Concept Study of Maintenance Therapy With Tasquinimod in Patients With Metastatic Castrate-resistant Prostate Cancer Who Are Not Progressing After a First Line Docetaxel Based Chemotherapy

Inclusion Criteria:

* Histologically documented prostate cancer with evidence of metastatic disease on radiological evaluation, with or without symptoms (defined according to the BPI scale, with use of analgesics or narcotics)
* Has received a first line docetaxel based chemotherapy (as a monotherapy) every 3 weeks schedule of administration with corticosteroids for a minimum of 6 cycles with a cumulative dose ≥360 mg/m2. Any combination with investigational or non investigational agent is prohibited
* Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1
* Docetaxel-related adverse effects must have been resolved to NCI-CTCAE v4.03 (Common Toxicity Criteria for Adverse Effects) Grade ≤1. Chemotherapy-induced alopecia and Grade 2 peripheral neuropathy are allowed
* No progressive disease at the end of docetaxel treatment defined according to RECIST criteria, no new lesion(s) assessed by bone scan and no elevated prostate specific antigen (PSA) for the three last tests with PSA3≤PSA2≤PSA1. The time between each PSA test should be preferably at least 14 days, however, a minimum of 7 days is acceptable.

Note: PSA value can be rounded to the nearest whole number if PSA\>10 ng/mL. If the PSA3 value is above the PSA2, a fourth PSA test will be performed. The PSA4 value should be below or equal to PSA2

* Last dose of docetaxel administered between 21 and 42 days before randomisation
* Chemical or surgical castration verified by levels of serum testosterone ≤50 ng/dL (1.75 nmol/L)

Exclusion Criteria:

* Has concurrent use of other anticancer agents or treatments, with the following exceptions: ongoing treatment with luteinising hormone-releasing hormone agonists or antagonists, denosumab or bisphosphonate (e.g., zoledronic acid) is permitted if started ≥4 weeks prior to Screening. Ongoing treatment should be kept at a stable dose regimen
* Has ongoing treatment with warfarin
* Had prior radiation therapy since starting docetaxel. Exceptions may be made for palliative non-myelosuppressive radiation therapy administered more than 2 weeks prior to randomisation
* Had prior strontium, samarium or radium therapy or prior treatment with tasquinimod, or any agents with antiangiogenic properties
* Has ongoing treatment with corticosteroids at \>10 mg/day prednisolone equivalent
* Has prostate cancer pain that warrants the initiation of radiotherapy or chemotherapy
* Has known brain or epidural metastases. Patients with previous medullary cord compression without any neurological deficit could be included
* Has a history of other malignancies, except adequately treated non-melanoma skin cancer or other solid tumours curatively treated, without evidence of disease for \>5 years