Intraperitoneal delivery of NanoOlaparib for disseminated late-stage cancer treatment.

BACKGROUND: PARP inhibitors, such as Olaparib, have advanced the treatment of ovarian cancer by providing patients with an effective and molecularly-targeted maintenance therapy. However, all orally-administered drugs, including Olaparib, must undergo first-pass metabolism. In contrast, a nanoparticle delivery system has the advantage of administering Olaparib directly into the peritoneal cavity for local treatment. Consequently, we sought to optimize the sustained-release formulation NanoOlaparib, previously deemed effective as an intravenous solid tumor treatment, for the local treatment of disseminated disease via intraperitoneal (i.p.) therapy. METHODS: The tumor cell line 404, which was derived from a Brca2 -/-, Tp53 -/-, Pten -/- genetically engineered mouse model, exhibited high sensitivity to Olaparib in vitro. It was chosen for use in developing an i.p. spread xenograft for testing nanotherapy efficacy in vivo. NanoOlaparib as a monotherapy or in combination with cisplatin was compared to oral Olaparib alone or in combination using two different dose schedules. A pilot biodistribution study was performed to determine drug accumulation in various organs following i.p. administration. RESULTS: Daily administration of NanoOlaparib reduced tumor growth and decreased the variability of the treatment response observed with daily oral Olaparib administration. However, systemic toxicity was observed in both the NanoOlaparib and vehicle (empty nanoparticle) treated groups. Scaling back the administration to twice weekly was well tolerated up to 100 mg/kg but reduced the effect on tumor growth. Biodistribution profiles indicated that NanoOlaparib began accumulating in tissues within an hour of administration and persisted for at least 72 hours after a single dose, exiting the peritoneal cavity faster than expected. CONCLUSION: NanoOlaparib must be modified for use against disseminated disease. Future avenues to develop NanoOlaparib as an i.p. therapy include a modified surface-coating to retain it in the peritoneal cavity and prevent entry into systemic circulation, in addition to targeting moieties for localization in tumor cells.

In vitro analysis of PARP inhibitor nanoformulations.

PARP-l is a DNA repair protein that plays a role in a number of repair pathways and also helps in transcriptional regulation; thus PARP inhibitors (PARPi), such as olaparib and BMN-673, act by inhibiting DNA damage repair. This leads to an accumulation of deleterious mutations leading to genetic instability as a result of a number of cell replications. Currently, olaparib is only available in an oral form and has poor bioavailability, consequently leading to poor accumulation in the tumor due to first-pass metabolism. Therefore, in the present study, an injectable nanoparticle formulation of olaparib was created that offers a delivery route in which the drug would be fully bioavailable in the vasculature, suggesting greater tumor accumulation. Our results illustrated that injectable nanoformulations of olaparib and BMN-673, a next generation PARPi, could be developed, and an efficacy test indicated that BMN-673 is a much more potent PARPi than olaparib. The success of these molecular inhibitors as a monotherapy in inhibiting colony formation suggests enhanced efficacy of these treatments in combination with other therapies, even in tumors which have developed resistance.

Nanoformulation of Olaparib Amplifies PARP Inhibition and Sensitizes PTEN/TP53-Deficient Prostate Cancer to Radiation.

The use of PARP inhibitors in combination with radiotherapy is a promising strategy to locally enhance DNA damage in tumors. Here we show that radiation-resistant cells and tumors derived from a Pten/Trp53-deficient mouse model of advanced prostate cancer are rendered radiation sensitive following treatment with NanoOlaparib, a lipid-based injectable nanoformulation of olaparib. This enhancement in radiosensitivity is accompanied by radiation dose-dependent changes in γ-H2AX expression and is specific to NanoOlaparib alone. In animals, twice-weekly intravenous administration of NanoOlaparib results in significant tumor growth inhibition, whereas previous studies of oral olaparib as monotherapy have shown no therapeutic efficacy. When NanoOlaparib is administered prior to radiation, a single dose of radiation is sufficient to triple the median mouse survival time compared to radiation only controls. Half of mice treated with NanoOlaparib + radiation achieved a complete response over the 13-week study duration. Using ferumoxytol as a surrogate nanoparticle, MRI studies revealed that NanoOlaparib enhances the intratumoral accumulation of systemically administered nanoparticles. NanoOlaparib-treated tumors showed up to 19-fold higher nanoparticle accumulation compared to untreated and radiation-only controls, suggesting that the in vivo efficacy of NanoOlaparib may be potentiated by its ability to enhance its own accumulation. Together, these data suggest that NanoOlaparib may be a promising new strategy for enhancing the radiosensitivity of radiation-resistant tumors lacking BRCA mutations, such as those with PTEN and TP53 deletions. Mol Cancer Ther; 16(7); 1279-89. ©2017 AACR.

Generation of Dose-Response Curves and Improved IC50s for PARP Inhibitor Nanoformulations.

Poly(ADP-ribose) polymerase (PARP) inhibitors that target DNA damage repair pathways in cancer cells are increasingly attractive for treating several cancers. Determining the half maximal inhibitory concentration (IC50) of these molecular inhibitors in cell lines is crucial for further dosing for in vivo experiments. Typically these in vitro assays are conducted for 24-72 h; however, PARP inhibitors exhibit cytotoxicity based on the inability to repair DNA damage and thus the accumulation of deleterious mutations takes place over longer times. Therefore, in order to determine a relevant dose response, the time frame of the assay must be modified to account for the time required for the cells to exhibit effects from the treatment. Here, we describe two techniques for generating both short- and long-term dose-response curves for both free PARP inhibitors and nanoparticle formulations of these drugs.

Simultaneous delivery of cytotoxic and biologic therapeutics using nanophotoactivatable liposomes enhances treatment efficacy in a mouse model of pancreatic cancer.

A lack of intracellular delivery systems has limited the use of biologics such as monoclonal antibodies (mAb) that abrogate molecular signaling pathways activated to promote escape from cancer treatment. We hypothesized that intracellular co-delivery of the photocytotoxic chromophore benzoporphyrin derivative monoacid A (BPD) and the anti-VEGF mAb bevacizumab in a nanophotoactivatable liposome (nanoPAL) might enhance the efficacy of photodynamic therapy (PDT) combined with suppression of VEGF-mediated signaling pathways. As a proof-of-concept we found that nanoPAL-PDT induced enhanced extra- and intracellular bevacizumab delivery and enhanced acute cytotoxicity in vitro. In an in vivo subcutaneous mouse model of pancreatic ductal adenocarcinoma, nanoPAL-PDT achieved significantly enhanced tumor reduction. We attribute this to the optimal incorporation of insoluble BPD into the lipid bilayer, enhancing photocytotoxicity, and the simultaneous spatiotemporal delivery of bevacizumab, ensuring efficient neutralization of the rapid but transient burst of VEGF following PDT. From the Clinical Editor: Most patients with pancreatic ductal adenocarcinoma (PDAC) by the time present the disease it is very advanced, which unavoidably translates to poor survival. For these patients, use of traditional chemotherapy often becomes ineffective due to tumor resistance to drugs. Photodynamic therapy (PDT) can be an effective modality against chemo-resistant cancers. In this article, the authors investigated the co-delivery of a photocytotoxic agent and anti-VEGF mAb using liposomes. This combination was shown to results in enhanced tumor killing. This method should be applicable to other combination of treatments.

Light-Controlled Delivery of Monoclonal Antibodies for Targeted Photoinactivation of Ki-67.

The selective inhibition of intracellular and nuclear molecules such as Ki-67 holds great promise for the treatment of cancer and other diseases. However, the choice of the target protein and the intracellular delivery of the functional agent remain crucial challenges. Main hurdles are (a) an effective delivery into cells, (b) endosomal escape of the delivered agents, and (c) an effective, externally triggered destruction of cells. Here we show a light-controlled two-step approach for selective cellular delivery and cell elimination of proliferating cells. Three different cell-penetrating nano constructs, including liposomes, conjugates with the nuclear localization sequence (NLS), and conjugates with the cell penetrating peptide Pep-1, delivered the light activatable antibody conjugate TuBB-9-FITC, which targets the proliferation associated protein Ki-67. HeLa cells were treated with the photosensitizer benzoporphyrin monoacid derivative (BPD) and the antibody constructs. In the first optically controlled step, activation of BPD at 690 nm triggered a controlled endosomal escape of the TuBB-9-FITC constructs. In more than 75% of Ki-67 positive, irradiated cells TuBB-9-FITC antibodies relocated within 24 h from cytoplasmic organelles to the cell nucleus and bound to Ki-67. After a second light irradiation at 490 nm, which activated FITC, cell viability decreased to approximately 13%. Our study shows an effective targeting strategy, which uses light-controlled endosomal escape and the light inactivation of Ki-67 for cell elimination. The fact that liposomal or peptide-assisted delivery give similar results leads to the additional conclusion that an effective mechanism for endosomal escape leaves greater variability for the choice of the delivery agent.

PARP inhibitors: A new era of targeted therapy.

Personalized medicine seeks to utilize targeted therapies with increased selectivity and efficacy in preselected patient cohorts. One such molecularly targeted therapy is enabled by inhibiting the enzyme poly(ADP-ribose) polymerase (PARP) by small molecule inhibitors in tumors which have a defect in the homologous DNA recombination pathway, most characteristically due to BRCA mutations. Olaparib, a highly potent PARP inhibitor, has recently been the approved for ovarian cancer therapy by the FDA and European commission in patients with platinum-sensitive, recurrent, high-grade serous ovarian cancer with BRCA1 or BRCA2 mutations. Currently, clinical trials with several PARP inhibitors are being conducted to assess the toxicities, the efficacies and the benefit of the drugs as monotherapies or combined with radiation or other chemotherapeutic agents, in ovarian, breast, prostate, rectal, lung, pancreatic, peritoneal, head and neck, brain, squamous cell carcinomas and sarcomas, to list a few. In this review, our focus is to outline the emerging molecular mechanisms, preclinical evidence and clinical applications of PARP inhibitors especially in nonBRCA cancers, and review the combination strategies compatible with PARP inhibitor therapy.