Extended topoisomerase 1 inhibition through liposomal irinotecan results in improved efficacy over topotecan and irinotecan in models of small-cell lung cancer.

Liposomal irinotecan (irinotecan liposome injection, nal-IRI), a liposomal formulation of irinotecan, is designed for extended circulation relative to irinotecan and for exploiting discontinuous tumor vasculature for enhanced drug delivery to tumors. Following tumor deposition, nal-IRI is taken up by phagocytic cells followed by irinotecan release and conversion to its active metabolite, SN-38. Sustained inhibition of topoisomerase 1 by extended SN-38 exposure as a result of delivery by nal-IRI is hypothesized to enable superior antitumor activity compared with traditional topoisomerase 1 inhibitors such as conventional irinotecan and topotecan. We evaluated the antitumor activity of nal-IRI compared with irinotecan and topotecan in preclinical models of small-cell lung cancer (SCLC) including in a model pretreated with carboplatin and etoposide, a first-line regimen used in SCLC. Nal-IRI demonstrated antitumor activity in xenograft models of SCLC at clinically relevant dose levels, and resulted in complete or partial responses in DMS-53, DMS-114, and NCI-H1048 cell line-derived models as well as in three patient-derived xenograft models. The antitumor activity of nal-IRI was superior to that of topotecan in all models tested, which generally exhibited limited control of tumor growth and was superior to irinotecan in four out of five models. Further, nal-IRI demonstrated antitumor activity in tumors that progressed following treatment with topotecan or irinotecan, and demonstrated significantly greater antitumor activity than both topotecan and irinotecan in NCI-H1048 tumors that had progressed on previous carboplatin plus etoposide treatment. These results support the clinical development of nal-IRI in patients with SCLC.

HER2-targeted liposomal doxorubicin displays enhanced anti-tumorigenic effects without associated cardiotoxicity.

Anthracycline-based regimens are a mainstay of early breast cancer therapy, however their use is limited by cardiac toxicity. The potential for cardiotoxicity is a major consideration in the design and development of combinatorial therapies incorporating anthracyclines and agents that target the HER2-mediated signaling pathway, such as trastuzumab. In this regard, HER2-targeted liposomal doxorubicin was developed to provide clinical benefit by both reducing the cardiotoxicity observed with anthracyclines and enhancing the therapeutic potential of HER2-based therapies that are currently available for HER2-overexpressing cancers. While documenting the enhanced therapeutic potential of HER2-targeted liposomal doxorubicin can be done with existing models, there has been no validated human cardiac cell-based assay system to rigorously assess the cardiotoxicity of anthracyclines. To understand if HER2-targeting of liposomal doxorubicin is possible with a favorable cardiac safety profile, we applied a human stem cell-derived cardiomyocyte platform to evaluate the doxorubicin exposure of human cardiac cells to HER2-targeted liposomal doxorubicin. To the best of our knowledge, this is the first known application of a stem cell-derived system for evaluating preclinical cardiotoxicity of an investigational agent. We demonstrate that HER2-targeted liposomal doxorubicin has little or no uptake into human cardiomyocytes, does not inhibit HER2-mediated signaling, results in little or no evidence of cardiomyocyte cell death or dysfunction, and retains the low penetration into heart tissue of liposomal doxorubicin. Taken together, this data ultimately led to the clinical decision to advance this drug to Phase I clinical testing, which is now ongoing as a single agent in HER2-expressing cancers.

64Cu-MM-302 Positron Emission Tomography Quantifies Variability of Enhanced Permeability and Retention of Nanoparticles in Relation to Treatment Response in Patients with Metastatic Breast Cancer.

Purpose: Therapeutic nanoparticles are designed to deliver their drug payloads through enhanced permeability and retention (EPR) in solid tumors. The extent of EPR and its variability in human tumors is highly debated and has been proposed as an explanation for variable responses to therapeutic nanoparticles in clinical studies.Experimental Design: We assessed the EPR effect in patients using a 64Cu-labeled nanoparticle, 64Cu-MM-302 (64Cu-labeled HER2-targeted PEGylated liposomal doxorubicin), and imaging by PET/CT. Nineteen patients with HER2-positive metastatic breast cancer underwent 2 to 3 PET/CT scans postadministration of 64Cu-MM-302 as part of a clinical trial of MM-302 plus trastuzumab with and without cyclophosphamide (NCT01304797).Results: Significant background uptake of 64Cu-MM-302 was observed in liver and spleen. Tumor accumulation of 64Cu-MM-302 at 24 to 48 hours varied 35-fold (0.52-18.5 %ID/kg), including deposition in bone and brain lesions, and was independent of systemic plasma exposure. Computational analysis quantified rates of deposition and washout, indicating peak liposome deposition at 24 to 48 hours. Patients were classified on the basis of 64Cu-MM-302 lesion deposition using a cut-off point that is comparable with a response threshold in preclinical studies. In a retrospective exploratory analysis of patient outcomes relating to drug levels in tumor lesions, high 64Cu-MM-302 deposition was associated with more favorable treatment outcomes (HR = 0.42).Conclusions: These findings provide important evidence and quantification of the EPR effect in human metastatic tumors and support imaging nanoparticle deposition in tumors as a potential means to identify patients well suited for treatment with therapeutic nanoparticles. Clin Cancer Res; 23(15); 4190-202. ©2017 AACR.

Dual HER2 Targeting with Trastuzumab and Liposomal-Encapsulated Doxorubicin (MM-302) Demonstrates Synergistic Antitumor Activity in Breast and Gastric Cancer.

Trastuzumab is the standard of care for HER2-positive breast cancer patients, markedly improving disease-free and overall survival. Combined with chemotherapy, it enhances patient outcomes, but cardiotoxicity due to the trastuzumab treatment poses a serious adverse effect. MM-302 is a HER2-targeted PEGylated liposome that encapsulates doxorubicin to facilitate its delivery to HER2-overexpressing tumor cells while limiting exposure to nontarget tissues, including the heart. In this study, we evaluated the feasibility and preclinical activity of combining MM-302 with trastuzumab. MM-302 and trastuzumab target different domains of the HER2 receptor and thus could simultaneously bind HER2-overexpressing tumor cells in vitro and in vivo. Furthermore, trastuzumab did not disrupt the mechanism of action of MM-302 in delivering doxorubicin to the n0ucleus and inducing DNA damage. Reciprocally, MM-302 did not interfere with the ability of trastuzumab to block prosurvival p-Akt signaling. Interestingly, coadministration of the two agents acutely increased the deposition of MM-302 in human xenograft tumors and subsequently increased the expression of the DNA damage marker p-p53. Finally, the combination of MM-302 and trastuzumab induced synergistic antitumor activity in HER2-overexpressing xenograft models of breast and gastric cancer. Collectively, our findings highlight a novel combination therapy that efficiently targets HER2-overexpressing cells through multiple mechanisms and support the ongoing investigation of combined MM-302/trastuzumab therapy for HER2-positive metastatic breast cancer in a randomized phase II clinical trial.