Giulia Dellavedova

The PARP1 Inhibitor AZD5305 Impairs Ovarian Adenocarcinoma Progression and Visceral Metastases in Patient-derived Xenografts Alone and in Combination with Carboplatin

PARP inhibitors (PARPi) have changed the management of patients with ovarian cancer and their effectiveness has been demonstrated especially in homologous recombination repair–deficient tumors. These first-generation drugs target PARP1, but also PARP2 and other family members potentially responsible for adverse effects that limit their therapeutic potential and restrict their use in combination with chemotherapeutic agents. We investigated ovarian cancer patient-derived xenografts (OC-PDXs) to assess whether malignant progression could be impaired by a novel inhibitor selective for PARP1 (AZD5305) and to assess the potential of its combination with carboplatin (CPT), the standard-of-care for patients with ovarian cancer. In BRCA-mutated OC-PDXs, AZD5305 achieved greater tumor regressions and longer duration of response as well as a superior impairment of visceral metastasis and improved survival benefit compared with the first-generation dual PARP1/2 inhibitors. The combination of AZD5305 plus CPT was more efficacious than single agents. Subcutaneously growing tumors experienced regression that persisted after therapy stopped. Combination efficacy was greater against tumors that did not respond well to platinum, even at a dose at which AZD5305 monotherapy was ineffective. The combination therapy impaired metastatic dissemination and significantly prolonged the lifespan of mice bearing OC-PDXs in their abdomen. This combination benefit was evident even when CPT was used at suboptimal doses, and was superior to full-dose platinum treatment. These preclinical studies demonstrate that the PARP1-selective inhibitor AZD5305 retains and improves the therapeutic benefit of the first-generation PARPi, providing an opportunity to maximize benefits for this class of anticancer agents. Significance: Selective PARP1i AZD5305 can exceed the efficacy of first-generation PARPi, which target both PARP1 and PARP2, and potentiates the efficacy of CPT when given in combination. AZD5305 alone or in combination with platinum delayed visceral metastasis, ultimately extending the lifespan of OC-PDX–bearing mice. These preclinical models mimic the progression of the disease occurring in patients after debulking surgery, and are translationally relevant.

The DNA-PK Inhibitor AZD7648 Sensitizes Patient-Derived Ovarian Cancer Xenografts to Pegylated Liposomal Doxorubicin and Olaparib Preventing Abdominal Metastases

Abstract Ovarian cancer is the deadliest gynecologic cancer, with a 5-year survival rate of 30%, when the disease has spread throughout the peritoneal cavity. We investigated the efficacy to delay disease progression by the DNA-dependent protein kinase (DNA-PK) inhibitor AZD7648, administered in combination with two of the therapeutic options for patient management: either pegylated liposomal doxorubicin (PLD) or the PARP inhibitor olaparib. Patient-derived ovarian cancer xenografts (OC-PDX) were transplanted subcutaneously to evaluate the effect of treatment on tumor growth, or orthotopically in the peritoneal cavity to evaluate the effect on metastatic spread. AZD7648 was administered orally in combination with PLD (dosed intravenously) or with olaparib (orally). To prove the inhibition of DNA-PK in the tumors, we measured pDNA-PKcs, pRPA32, and γH2AX, biomarkers of DNA-PK activity. AZD7648 enhanced the therapeutic efficacy of PLD in all the OC-PDXs tested, regardless of their BRCA status or sensitivity to cisplatin or PLD. The treatment caused disease stabilization, which persisted despite therapy discontinuation for tumors growing subcutaneously, and significantly impaired the abdominal metastatic dissemination, prolonging the lifespan of mice implanted orthotopically. AZD7648 potentiated the efficacy of olaparib in BRCA-deficient OC-PDXs but did not sensitize BRCA-proficient OC-PDXs to olaparib, despite an equivalent inhibition of DNA-PK, suggesting the need of a preexisting olaparib activity to benefit from the addition of AZD7648. This work suggests that AZD7648, an inhibitor of DNA-PK, dosed in combination with PLD or olaparib is an exciting therapeutic option that could benefit patients with ovarian cancer and should be explored in clinical trials.