53BP1 as a potential predictor of response in PARP inhibitor-treated homologous recombination-deficient ovarian cancer

OBJECTIVE

Poly(ADP-ribose) polymerase (PARP) inhibitors have shown substantial activity in homologous recombination- (HR-) deficient ovarian cancer and are undergoing testing in other HR-deficient tumors. For reasons that are incompletely understood, not all patients with HR-deficient cancers respond to these agents. Preclinical studies have demonstrated that changes in alternative DNA repair pathways affect PARP inhibitor (PARPi) sensitivity in ovarian cancer models. This has not previously been assessed in the clinical setting.

METHODS

Clonogenic and plasmid-based HR repair assays were performed to compare BRCA1-mutant COV362 ovarian cancer cells with or without 53BP1 gene deletion. Archival biopsies from ovarian cancer patients in the phase I, open-label clinical trial of PARPi ABT-767 were stained for PARP1, RAD51, 53BP1 and multiple components of the nonhomologous end-joining (NHEJ) DNA repair pathway. Modified histochemistry- (H-) scores were determined for each repair protein in each sample. HRD score was determined from tumor DNA.

RESULTS

53BP1 deletion increased HR in BRCA1-mutant COV362 cells and decreased PARPi sensitivity in vitro. In 36 women with relapsed ovarian cancer, responses to the PARPi ABT-767 were observed exclusively in cancers with HR deficiency. In this subset, 7 of 18 patients (39%) had objective responses. The actual HRD score did not further correlate with change from baseline tumor volume (r = 0.050; p = 0.87). However, in the HR-deficient subset, decreased 53BP1 H-score was associated with decreased antitumor efficacy of ABT-767 (r = -0.69, p = 0.004).

CONCLUSION

Differences in complementary repair pathways, particularly 53BP1, correlate with PARPi response of HR-deficient ovarian cancers.

A phase 1 study of PARP-inhibitor ABT-767 in advanced solid tumors with BRCA1/2 mutations and high-grade serous ovarian, fallopian tube, or primary peritoneal cancer

Purpose This phase 1 study examined safety, pharmacokinetics (PK), and efficacy of the poly(ADP-ribose) polymerase (PARP) inhibitor ABT-767 in patients with advanced solid tumors and BRCA1/2 mutations or with high-grade serous ovarian, fallopian tube, or primary peritoneal cancer. Methods Patients received ABT-767 monotherapy orally until disease progression or unacceptable toxicity. Dose was escalated from 20 mg once daily to 500 mg twice daily (BID). Dose-limiting toxicities, recommended phase 2 dose (RP2D), food effect, objective response rate, and biomarkers predicting response were determined. Results Ninety-three patients were treated with ABT-767; 80 had a primary diagnosis of ovarian cancer. ABT-767 demonstrated dose-proportional PK up to 500 mg BID and half-life of ~2 h. Food had no effect on ABT-767 bioavailability. Most common grade 3/4 treatment-related adverse events were nausea, fatigue, decreased appetite, and anemia. Anemia showed dose-dependent increase. RP2D was 400 mg BID. Objective response rate by RECIST 1.1 was 21% (17/80) in all evaluable patients and 20% (14/71) in evaluable patients with ovarian cancer. Response rate by RECIST 1.1 and/or CA-125 was 30% (24/80) in patients with ovarian cancer. Mutations in BRCA1 or BRCA2, homologous recombination deficiency (HRD), and platinum sensitivity were associated with tumor response. Median progression-free survival was longer for HRD positive (6.7 months) versus HRD negative patients (1.8 months) with ovarian cancer. Conclusions ABT-767 had an acceptable safety profile up to the established RP2D of 400 mg BID and dose-proportional PK. Patients with BRCA1 or BRCA2 mutation, HRD positivity, and platinum sensitivity were more sensitive to ABT-767.

Bleomycin-Induced Pulmonary Changes on Restaging Computed Tomography Scans in Two Thirds of Testicular Cancer Patients Show No Correlation With Fibrosis Markers

BACKGROUND

In metastatic testicular cancer patients treated with bleomycin, etoposide, and cisplatin (BEP) chemotherapy, bleomycin-induced pneumonitis is a well-known and potentially fatal side effect. We sought to determine the prevalence of lesions as signs of bleomycin-induced pulmonary changes on restaging computed tomography (CT) scans after treatment and to ascertain whether fibrosis markers were predictive of these changes.

PATIENTS AND METHODS

This prospective nonrandomized cohort study included metastatic testicular cancer patients, 18-50 years of age, treated with BEP chemotherapy. Restaging CT scans were examined for lesions as signs of bleomycin-induced pulmonary changes by two independent radiologists and graded as minor, moderate, or severe. Plasma samples were collected before, during, and after treatment and were quantified for transforming growth factor-β1 (TGF-β1), growth differentiation factor-15 (GDF-15), and high-sensitivity C-reactive protein (hs-CRP).

RESULTS

In total, 66 patients were included: forty-five (68%) showed signs of bleomycin-induced pulmonary changes on the restaging CT scan, 37 of which were classified as minor and 8 as moderate. No differences in TGF-β1, GDF-15, or hs-CRP plasma levels were found between these groups.

CONCLUSION

Bleomycin-induced pulmonary changes are common on restaging CT scans after BEP chemotherapy for metastatic testicular cancer. Changes in TGF-β1, GDF-15, and hs-CRP plasma levels do not differ between patients with and without radiological lesions as signs of bleomycin-induced pulmonary changes and are therefore not helpful as predictive biomarkers.

IMPLICATIONS FOR PRACTICE

Bleomycin-induced pneumonitis (BIP) is a well-known and potentially fatal side effect in metastatic testicular cancer patients treated with bleomycin, etoposide, and cisplatin chemotherapy. Currently, the decision to discontinue bleomycin administration is made during treatment and is based on clinical signs. An upfront or early marker or biomarker that identifies patients likely to develop BIP would be preferable. This study found that bleomycin-induced pulmonary changes are common on restaging computed tomography scans and mostly resolve. No correlation was seen between these changes and fibrosis or inflammation markers (transforming growth factor-β1, growth differentiation factor-15, and high-sensitivity C-reactive protein).

89zr-GC1008 PET imaging and GC1008 treatment of recurrent glioma patients

2050

Background: Transforming growth factor-β (TGF-β) signaling is involved in glioma development. GC1008 is a monoclonal antibody that has demonstrated significant neutralization of all mammalian isoforms of TGF-β in preclinical models (Lonning, Curr Pharm Biotechnol 2011). The aim of this study was to investigate whether GC1008 uptake in brain tumors can be visualized using the 89Zirkonium (Zr)-GC1008 PET scan and to assess treatment outcome in patients with recurrent glioma treated with GC1008 (NCT01472731). Methods: Patients with WHO II-IV glioma who presented with recurrent disease were eligible. After iv administration of 37 MBq (5 mg) 89Zr-GC1008, 89Zr-GC1008 PET scans were performed on day 2 and day 4 post injection. Thereafter, patients were treated with 5 mg/kg GC1008 iv every 3 weeks. MRI scans were made for response evaluation after 3 courses or as clinically indicated. Results: Twelve patients with 1st-8th recurrent disease were included (10 glioblastoma, 1 anaplastic oligodendroglioma, 1 anaplastic astrocytoma), all underwent an 89Zr-GC1008 PET scan on day 4, 4 patients also underwent a PET scan on day 2 after tracer injection. Median SUVmax on day 4 was in tumor lesions 4.6 (range 1.5-13.9) and median SUVmean in normal brain tissue 0.3 (range 0.2-0.5). In 3 out of 4 patients who underwent a day 2 and day 4 whole body scan uptake decreased in most normal organs but not in tumor lesions, supporting tumor specific 89Zr-GC1008 uptake. No major toxicity of GC1008 treatment was observed, but all patients showed clinical and/or radiological progressive disease after 1-3 cycles. Median progression free survival was 61 days (range 25-80) and median overall survival 106 days (range 37-287+). Conclusions: 89Zr-GC1008 showed excellent uptake by recurrent gliomas. Clinical benefit of GC1008 treatment was not observed in this limited study population. Clinical trial information: 01472731.