No abstract

Purpose: LMB-100 is a recombinant immunotoxin (iTox) consisting of a mesothelin-binding Fab for targeting and a modified Pseudomonas exotoxin A payload. Preclinical studies showed that combining taxanes with iTox results in synergistic antitumor activity. The objectives of this phase I/II study were to determine the MTD of LMB-100 when administered with nanoalbumin bound (nab)-paclitaxel to patients with previously treated advanced pancreatic adenocarcinoma and to assess the objective response rate. Patients and Methods: Patients (n = 20) received fixed-dose nab-paclitaxel (125 mg/m2 on days 1 and 8) with LMB-100 (65 or 100 μg/kg on days 1, 3, and 5) in 21-day cycles for 1–3 cycles. Results: Fourteen patients were treated on the dose escalation and an additional six in the phase II expansion. MTD of 65 μg/kg was established for the combination. Dose-limiting toxicity resulting from capillary leak syndrome (CLS) was seen in two of five patients treated at 100 μg/kg and one of six evaluable phase I patients receiving the MTD. Severity of CLS was associated with increases in apoptotic circulating endothelial cells. LMB-100 exposure was unaffected by anti-LMB-100 antibody formation in five of 13 patients during cycle 2. Seven of 17 evaluable patients experienced >50% decrease in CA 19-9, including three with previous exposure to nab-paclitaxel. One patient developed an objective partial response. Patients with biomarker responses had higher tumor mesothelin expression. Conclusions: Although clinical activity was observed, the combination was not well tolerated and alternative drug combinations with LMB-100 will be pursued.

Cellular responses to low oxygen (hypoxia) are fundamental to normal physiology and to the pathology of many common diseases. Hypoxia-inducible factor (HIF) is central to this by enhancing the transcriptional activity of many hundreds of genes. The cellular response to HIF is cell-type-specific and is largely governed by the pre-existing epigenetic landscape. Prior to activation, HIF-binding sites and the promoters of HIF-target genes are already accessible, in contact with each other through chromatin looping and display markers of activity. However, hypoxia also modulates the epigenetic environment, both in parallel to and as a consequence of HIF activation. This occurs through a combination of oxygen-sensitive changes in enzyme activity, transcriptional activation of epigenetic modifiers, and localized recruitment to chromatin by HIF and activated RNApol2. These hypoxic changes in the chromatin environment may both contribute to and occur as a consequence of transcriptional regulation. Nevertheless, they have the capacity to both modulate and extend the transcriptional response to hypoxia.