Toca 511 (vocimagene amiretrorepvec) is an investigational nonlytic, retroviral replicating vector (RRV) that delivers a yeast cytosine deaminase, which converts subsequently administered courses of the investigational prodrug Toca FC (extended-release 5-fluorocytosine) into the antimetabolite 5-fluorouracil. Forty-five subjects with recurrent or progressive high-grade glioma were treated. The end points of this phase 1, open-label, ascending dose, multicenter trial included safety, efficacy, and molecular profiling; survival was compared to a matching subgroup from an external control. Overall survival for recurrent high-grade glioma was 13.6 months (95% confidence interval, 10.8 to 20.0) and was statistically improved relative to an external control (hazard ratio, 0.45; P = 0.003). Tumor samples from subjects surviving more than 52 weeks after Toca 511 delivery disproportionately displayed a survival-related mRNA expression signature, identifying a potential molecular signature that may correlate with treatment-related survival rather than being prognostic. Toca 511 and Toca FC show excellent tolerability, with RRV persisting in the tumor and RRV control systemically. The favorable assessment of Toca 511 and Toca FC supports confirmation in a randomized phase 2/3 trial (NCT02414165).

The alpha subunit (alpha) of RNA polymerase (RNAP) is critical for assembly of polymerase and positive control of transcription initiation in Escherichia coli. Here, we report that alpha also plays a role in transcription elongation, and this involves a direct interaction between alpha and NusA factor. During in vitro transcription without NusA, alpha interacts with the nascent RNA, as revealed by photocrosslinking. When NusA is present, RNA crosslinks to NusA rather than to alpha. We show that this NusA‐RNA interaction is diminished during transcription with an RNAP mutant that lacks the C‐terminus of alpha beyond amino acid 235, including the so‐called alpha CTD. The absence of alpha CTD also affects NusA's ability to enhance transcription pausing, termination at intrinsic terminators and anti‐termination by the phage lambda Q anti‐terminator, but not anti‐termination by the lambda N anti‐terminator. NusA functions are not recovered even when transcription with mutant RNAP is done with excess NusA, a condition which does restore NusA‐RNA crosslinking. By affinity chromatography, we show that NusA interacts directly with alpha, and also with beta and beta’, but not with mutant alpha. Hence, alpha‐NusA interaction is vital for the control of transcript elongation and termination.

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