Epithelial ovarian cancer (EOC) is the most lethal gynaecological malignancy causing 41900 deaths annually in Europe. The predominance of aggressive Type II tumours, which are characterised by a high frequency of p53 mutations, and primary or acquired resistance to platinum-based chemotherapy profoundly contribute to the high mortality rate. With current standard therapy the median overall survival of metastatic platinum-resistant (Pt-R) ovarian cancer patients is only 14 month. There is a pressing need for more effective, innovative treatment strategies to particularly improve survival in this subgroup of EOC patients. This is a drug strategy targeting a central driver of tumour aggressiveness and metastatic ability, namely mutant p53, via an innovative new Hsp90 (heat shock protein 90) inhibition mechanism. The most advanced, second-generation Hsp90 inhibitor will be used, Ganetespib. The first part (Phase I) of the GANNET53 trial will test the safety of Ganetespib in a new combination with standard chemotherapy (Paclitaxel weekly) in Pt-R EOC patients. The second part (randomised Phase II) will examine the efficacy of Ganetespib in combination with standard chemotherapy versus standard chemotherapy alone in EOC patients with Pt-R tumours.