Precise oncotropism is required for successful systemic administration of next-generation oncolytic measles viruses (MVs). We have previously established a system for efficient post-entry targeting by insertion of synthetic microRNA target sites (miRTS) into the MV genome, thereby repressing replication in the presence of cognate microRNAs. Thus, differential expression of microRNAs, as frequently observed in normal compared with malignant tissues, can be exploited to increase vector specificity and safety. Here we report the combination of miRTS for different microRNAs in a single vector to detarget pivotal organs at risk during systemic administration (liver, brain, gastrointestinal tract). Accordingly, miRTS for miR-122, miR-7 and miR-148a that are enriched in these tissues were inserted to create multi-tissue-detargeted MV (MV-EGFP(mtd)). Replication of MV-EGFP(mtd) is repressed in cell lines as well as in non-transformed primary human hepatocytes and liver slices expressing cognate microRNAs. Oncolytic potency of MV-EGFP(mtd) is retained in a model of pancreatic cancer in vitro and in vivo. This work is a proof-of-concept that favorable expression profiles of multiple microRNAs can be exploited concomitantly to reshape the tropism of MV without compromising oncolytic efficacy. This strategy can be adapted to different vectors and cancer entities for safe and efficient high-dose systemic administration in clinical trials.

The histone deacetylase inhibitor panobinostat has shown efficacy in phase-II and phase-III trials for multiple myeloma and has recently received market approval in combination with bortezomib and dexamethasone. Here, we retrospectively report our single center experience with panobinostat/bortezomib/dexamethasone (FVD) in a heavily pretreated patient population (n = 24) with a high degree of refractoriness to proteasome inhibitors (PI) and immunomodulatory drugs (IMiD). Median age was 67 years (range 49-87) and the median number of prior therapies was 5 (range 2-17). Fourteen patients (58%) had high-risk cytogenetic aberrations. Thirteen (54%) and 21 (88%) patients were refractory to PIs and IMiDs, respectively. Twelve patients (50%) were refractory to bortezomib and 7 (29%) to carfilzomib; 6 patients (25%) were refractory to both bortezomib and carfilzomib. In 21 patients evaluable for response, overall response rate (ORR; ≥PR) was 33% (7/21) and 81% (17/21) achieved at least stable disease. Median progression-free survival (PFS) and overall survival were 3.5 and 9.8 months, respectively. Significant differences between bortezomib-sensitive and -refractory patients were observed. In bortezomib-sensitive patients, median PFS was 6.3 months compared to 2.3 months in bortezomib-refractory patients (P < .001). Median overall survival was not reached vs 4.8 months (P = .046) in bortezomib-sensitive and bortezomib-refractory patients, respectively. The only patient refractory to carfilzomib but sensitive to bortezomib achieved very good partial remission and PFS of 6.3 months, suggesting discrete mechanisms of resistance to different PIs. As expected, thrombocytopenia and fatigue/asthenia occurred in nearly all patients (96% and 83%, respectively). Diarrhea was observed in only 19% of patients which compares favorably with the high rates of diarrhea reported in the PANORAMA trials. With panobinostat dose reductions in 67% of patients, FVD was tolerated by the majority of patients. In conclusion, FVD showed efficacy in a heavily pretreated, high-risk multiple myeloma population with a high degree of patients refractory to novel agents including PIs.

Measles viruses derived from the live-attenuated Edmonton-B vaccine lineage are currently investigated as novel anti-cancer therapeutics. In this context, tumor specificity and oncolytic potency are key determinants of the therapeutic index. Here, we describe a systematic and comprehensive analysis of a recently developed post-entry targeting strategy based on the incorporation of microRNA target sites (miRTS) into the measles virus genome. We have established viruses with target sites for different microRNA species in the 3′ untranslated regions of either the N, F, H, or L genes and generated viruses harboring microRNA target sites in multiple genes. We report critical importance of target-site positioning with proximal genomic positions effecting maximum vector control. No relevant additional effect of six versus three miRTS copies for the same microRNA species in terms of regulatory efficiency was observed. Moreover, we demonstrate that, depending on the microRNA species, viral mRNAs containing microRNA target sites are directly cleaved and/or translationally repressed in presence of cognate microRNAs. In conclusion, we report highly efficient control of measles virus replication with various miRTS positions for development of safe and efficient cancer virotherapy and provide insights into the mechanisms underlying microRNA-mediated vector control.