ORCHID: A phase II study of Olaparib in Metastatic Renal Cell Carcinoma Patients HarborIng a BAP1 or Other DNA Repair Gene Mutations

Background

DNA damage repair genes alterations (DDRa) are frequent events in renal cell carcinoma (RCC), including BAP1 and other DDRa. Olaparib is a poly ADP ribose polymerase inhibitor (PARPi) that is FDA-approved for the treatment of several malignancies with DDRa. Preclinical models demonstrated synthetic lethality with PARPi in RCC cell lines including BAP1 mutant lines. Here we report an interim analysis of the ORCHID study investigating the clinical activity of single agent olaparib in patients (pts) with advanced RCC (aRCC) harboring BAP1 other select DDRa.

Methods

We conducted a single center, single arm, investigator-initiated Phase 2 trial of olaparib in pts with aRCC. Eligible pts harbored select DDRa and had prior therapy with immune checkpoint inhibitors (ICIs) and/or VEGF-TKI. Pts were treated with olaparib at an initial dose of 150mg twice which was increased to 300mg twice daily after one month if well tolerated. The primary endpoint is disease control rate (DCR) by RECIST v1.1 (including complete response (CR), partial response (PR), and stable disease (SD) >6 months). Secondary endpoints included objective response rate (ORR), progression free survival (PFS), and safety.

Results

Eleven pts were enrolled with a median age of 59 years (48-72) including 9 pts with clear cell RCC and 2 pts with unclassified RCC. Most pts had BAP1 mutations (Table). 36% of pts had history of brain metastasis. Median number of prior lines of therapies was 2 (1-6) and all pts received prior ICI. The study met the pre-specified Simon’s 2 stage design for the first stage with 22% DCR in the evaluable pts (2/9), including deep PR (>70% reduction in tumor volume) and SD of 10 months. Both pts harbored BAP1 mutations. An additional pt with BRCA1 mutation had 20% decrease in measurable disease. There were no treatment related adverse events resulting in study discontinuation.

Conclusions

This is the first study investigating single agent PARPi in RCC with the interim trial analysis indicating promising activity of olaparib in aRCC pts with BAP1 mutations including one pt with deep PR. These results support further development of PARPi in this setting.

ATR Inhibition Potentiates the Radiation-induced Inflammatory Tumor Microenvironment

PURPOSE

ATR inhibitors (ATRi) are in early phase clinical trials and have been shown to sensitize to chemotherapy and radiotherapy preclinically. Limited data have been published about the effect of these drugs on the tumor microenvironment.Experimental Design: We used an immunocompetent mouse model of HPV-driven malignancies to investigate the ATR inhibitor AZD6738 in combination with fractionated radiation (RT). Gene expression analysis and flow cytometry were performed posttherapy.

RESULTS

Significant radiosensitization to RT by ATRi was observed alongside a marked increase in immune cell infiltration. We identified increased numbers of CD3+ and NK cells, but most of this infiltrate was composed of myeloid cells. ATRi plus radiation produced a gene expression signature matching a type I/II IFN response, with upregulation of genes playing a role in nucleic acid sensing. Increased MHC I levels were observed on tumor cells, with transcript-level data indicating increased antigen processing and presentation within the tumor. Significant modulation of cytokine gene expression (particularly CCL2, CCL5, and CXCL10) was found in vivo, with in vitro data indicating CCL3, CCL5, and CXCL10 are produced from tumor cells after ATRi + RT.

CONCLUSIONS

We show that DNA damage by ATRi and RT leads to an IFN response through activation of nucleic acid-sensing pathways. This triggers increased antigen presentation and innate immune cell infiltration. Further understanding of the effect of this combination on the immune response may allow modulation of these effects to maximize tumor control through antitumor immunity.

Targeting DNA Repair in Cancer: Beyond PARP Inhibitors

Germline aberrations in critical DNA-repair and DNA damage-response (DDR) genes cause cancer predisposition, whereas various tumors harbor somatic mutations causing defective DDR/DNA repair. The concept of synthetic lethality can be exploited in such malignancies, as exemplified by approval of poly(ADP-ribose) polymerase inhibitors for treating BRCA1/2-mutated ovarian cancers. Herein, we detail how cellular DDR processes engage various proteins that sense DNA damage, initiate signaling pathways to promote cell-cycle checkpoint activation, trigger apoptosis, and coordinate DNA repair. We focus on novel therapeutic strategies targeting promising DDR targets and discuss challenges of patient selection and the development of rational drug combinations.

SIGNIFICANCE

Various inhibitors of DDR components are in preclinical and clinical development. A thorough understanding of DDR pathway complexities must now be combined with strategies and lessons learned from the successful registration of PARP inhibitors in order to fully exploit the potential of DDR inhibitors and to ensure their long-term clinical success. Cancer Discov; 7(1); 20-37. ©2016 AACR.

The actin depolymerizing factor (ADF)/cofilin signaling pathway and DNA damage responses in cancer

The actin depolymerizing factor (ADF)/cofilin protein family is essential for actin dynamics, cell division, chemotaxis and tumor metastasis. Cofilin-1 (CFL-1) is a primary non-muscle isoform of the ADF/cofilin protein family accelerating the actin filamental turnover in vitro and in vivo. In response to environmental stimulation, CFL-1 enters the nucleus to regulate the actin dynamics. Although the purpose of this cytoplasm-nucleus transition remains unclear, it is speculated that the interaction between CFL-1 and DNA may influence various biological responses, including DNA damage repair. In this review, we will discuss the possible involvement of CFL-1 in DNA damage responses (DDR) induced by ionizing radiation (IR), and the implications for cancer radiotherapy.

Loss of ATM/Chk2/p53 pathway components accelerates tumor development and contributes to radiation resistance in gliomas

Maintenance of genomic integrity is essential for adult tissue homeostasis and defects in the DNA-damage response (DDR) machinery are linked to numerous pathologies including cancer. Here, we present evidence that the DDR exerts tumor suppressor activity in gliomas. We show that genes encoding components of the DDR pathway are frequently altered in human gliomas and that loss of elements of the ATM/Chk2/p53 cascade accelerates tumor formation in a glioma mouse model. We demonstrate that Chk2 is required for glioma response to ionizing radiation in vivo and is necessary for DNA-damage checkpoints in the neuronal stem cell compartment. Finally, we observed that the DDR is constitutively activated in a subset of human GBMs, and such activation correlates with regions of hypoxia.

Discoidin domain receptor 1 functions in axon extension of cerebellar granule neurons

In the developing cerebellum, granule neuron axon outgrowth is a key step toward establishing proper connections with Purkinje neurons, the principal output neuron of the cerebellum. During a search for genes that function in this process, we identified a receptor tyrosine kinase discoidin domain receptor 1 (DDR1) expressed in granule cells throughout their development. Overexpression of a dominant-negative form of DDR1 in immature granule cells results in severe reduction of neurite outgrowth in vitro, in dissociated primary culture, and in vivo, in organotypic slices of neonatal cerebellum. Granule cells that fail to extend axons are positive for differentiation markers such as TAG-1 and the neuron-specific class III beta-tubulin, suggesting that development is affected after granule cells commit to terminal differentiation. DDR1 activation appears to be mediated by its ligand, collagen, which is localized to the pial layer of the developing cerebellum, thereby leading to granule cell parallel fiber extension. Our results therefore indicate that collagen-DDR1 signaling is essential for granule neuron axon formation and further suggest a unique role of pia in cerebellar cortex histogenesis.