Application of Liquid Biopsies in Cancer Targeted Therapy

As a growing body of evidence demonstrates intertumoral and intratumoral heterogeneity and clonal evolution, both during carcinogenesis and also throughout treatment resulting in acquired drug resistance, the utility of blood-based assays or "liquid biopsies" is becoming increasingly recognized in clinical practice and trial design. "Liquid biopsies" provide a less invasive approach to the current gold standard of interrogating tumors by tissue biopsies, which are frequently unfeasible, associated with morbidity, and cannot be performed as often.

Targeting the androgen receptor pathway in castration-resistant prostate cancer: progresses and prospects

Androgen receptor (AR) signaling is a critical pathway for prostate cancer cells, and androgen-deprivation therapy (ADT) remains the principal treatment for patients with locally advanced and metastatic disease. However, over time, most tumors become resistant to ADT. The view of castration-resistant prostate cancer (CRPC) has changed dramatically in the last several years. Progress in understanding the disease biology and mechanisms of castration resistance led to significant advancements and to paradigm shift in the treatment. Accumulating evidence showed that prostate cancers develop adaptive mechanisms for maintaining AR signaling to allow for survival and further evolution. The aim of this review is to summarize molecular mechanisms of castration resistance and provide an update in the development of novel agents and strategies to more effectively target the AR signaling pathway.

Abstract P2-09-02: BMN 673 is a PARP inhibitor in clinical development for the treatment of breast cancer patients with deleterious germline BRCA 1 and 2 mutations

Background: BMN 673 is the most potent and specific inhibitor of poly-ADP ribose polymerase (PARP) 1 and 2 in clinical development (IC50<1nM). In BRCA-related tumors, which are genetically dependent on PARP-mediated DNA repair by base excision repair, PARP inhibition induces synthetic lethality. Initial phase 1 results have been presented (de Bono et al JCO 31:5s, 2013 suppl; abstr 2580), showing good tolerability and anti-tumor activity with an MTD on a daily, oral dosing schedule of 1000 μ/day.

Methods: In this 2-stage study, patients with solid tumors including BRCA-related cancers, were enrolled during dose-escalation followed by an expansion phase at the MTD in breast, ovarian, and pancreatic cancer patients with deleterious germline BRCA mutations and in small cell lung cancer and Ewing sarcoma patients to further characterize safety and efficacy. This abstract summarizes demographics and safety for all patients and efficacy for patients with BRCA-related cancers.

Results: As of 17May2013, a total of 1 pancreatic, 18 breast (17F/1M), and 28 ovarian cancer pts with germline BRCA mutations were enrolled at doses from 100-1100 μg/day. All breast cancer patients were treated from 900-1100 μg/day. The median (range) age for all 70 patients is 51.5 (18-81), PS 0 (0-1) and # of prior therapies 4 (1-13), with 47 patients having deleterious BRCA mutations. An MTD of 1000 μg/day was established with thrombocytopenia being dose-limiting. Related adverse events occurring in > 10% of all 70 patients included fatigue, nausea, alopecia, anemia, thrombocytopenia and neutropenia. One patient has had related grade 4 thrombocytopenia. Grade 3 related AE's included fatigue in 1 patient (1%), anemia and thrombocytopenia in 9 each (13%) and neutropenia in 4 (6%). Dose reductions occurred in 11 pts due to myelosuppression. No patients discontinued for adverse events.

Response in Germline BRCA PatientsBRCA Tumor TypeNDose Range (μ/day)ResponseBreast18900-11001CR/6PR/5SD≥12 weeksOvarian28100-11001CR/10PR/19GCIG/4SD≥24 weeksPancreas110001 SD ≥ 12weeksTwo of 2 BRCA breast responders had responded to prior platinum while 0 of 4 non-responders to prior platinum responded to BMN 673. Five of 12 breast cancer pts with no prior platinum have responded.

Conclusions: BMN 673 is well tolerated with impressive anti-tumor activity in pts with deleterious germ line BRCA mutations. Myelosuppression and fatigue are the primary side effects associated with need for dose reduction. A phase 3 trial in metastatic breast cancer patients with deleterious germ line BRCA mutations is planned with single-agent, once-daily oral dosing of 1000 μg (1 mg) per day.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P2-09-02.