Resistance to Pyrrolobenzodiazepine Dimers Is Associated with SLFN11 Downregulation and Can Be Reversed through Inhibition of ATR.

Resistance to antibody-drug conjugates (ADCs) has been observed in both preclinical models and clinical studies. However, mechanisms of resistance to pyrrolobenzodiazepine (PBD)-conjugated ADCs have not been well characterized and thus, this study was designed to investigate development of resistance to PBD dimer warheads and PBD-conjugated ADCs. We established a PBD-resistant cell line, 361-PBDr, by treating human breast cancer MDA-MB-361 cells with gradually increasing concentrations of SG3199, the PBD dimer released from the PBD drug-linker tesirine. 361-PBDr cells were over 20-fold less sensitive to SG3199 compared with parental cells and were cross-resistant to other PBD warhead and ADCs conjugated with PBDs. Proteomic profiling revealed that downregulation of Schlafen family member 11 (SLFN11), a putative DNA/RNA helicase, sensitizing cancer cells to DNA-damaging agents, was associated with PBD resistance. Confirmatory studies demonstrated that siRNA knockdown of SLFN11 in multiple tumor cell lines conferred reduced sensitivity to SG3199 and PBD-conjugated ADCs. Treatment with EPZ011989, an EZH2 inhibitor, derepressed SLFN11 expression in 361-PBDr and other SLFN11-deficient tumor cells, and increased sensitivity to PBD and PBD-conjugated ADCs, indicating that the suppression of SLFN11 expression is associated with histone methylation as reported. Moreover, we demonstrated that combining an ataxia telangiectasia and Rad3-related protein (ATR) inhibitor, AZD6738, with SG3199 or PBD-based ADCs led to synergistic cytotoxicity in either resistant 361-PBDr cells or cells that SLFN11 was knocked down via siRNA. Collectively, these data provide insights into potential development of resistance to PBDs and PBD-conjugated ADCs, and more importantly, inform strategy development to overcome such resistance.

Synthesis and evaluation of pyrrolobenzodiazepine dimer antibody-drug conjugates with dual ß-glucuronide and dipeptide triggers.

Antibody-drug conjugates (ADCs) containing pyrrolobenzodiazepine (PBD) dimers are currently being evaluated in human oncology clinical trials with encouraging results. To further improve the therapeutic window, next-generation PBD drug-linker design has focused on the inclusion of additional tumor-selective triggers and use of lower-potency PBDs. ß-Glucuronidase is a well-known target for discovery prodrugs due to increased presence in tumor cells and microenvironment. In this study, a ß-glucuronidase cleavable cap was investigated at the PBD N10-position and compared with corresponding free imine ADCs. SG3600 (glucuronide) ADCs showed in vitro and in vivo efficacy/tolerability comparable to SG3400 (imine) ADCs, and good 50% inhibitory concentration differentials were observed in vitro between control non-antigen-targeted ADCs and targeted ADCs. Dependence on ß-glucuronidase for SG3600 activity was demonstrated through CRISPRCas9 knockdown studies and addition of exogenous ß-glucuronidase. SG3600 showed better serum stability, improved conjugation efficiency and was able to reach high drug-to-antibody ratio without aggregation.

Evaluation of Pharmacodynamic Responses to Cancer Therapeutic Agents Using DNA Damage Markers.

PURPOSE: We sought to examine the pharmacodynamic activation of the DNA damage response (DDR) pathway in tumors following anticancer treatment for confirmation of target engagement. EXPERIMENTAL DESIGN: We evaluated the time course and spatial activation of 3 protein biomarkers of DNA damage recognition and repair (γH2AX, pS343-Nbs1, and Rad51) simultaneously in a quantitative multiplex immunofluorescence assay (IFA) to assess DDR pathway activation in tumor tissues following exposure to DNA-damaging agents. RESULTS: Because of inherent biological variability, baseline DDR biomarker levels were evaluated in a colorectal cancer microarray to establish clinically relevant thresholds for pharmacodynamic activation. Xenograft-bearing mice and clinical colorectal tumor biopsies obtained from subjects exposed to DNA-damaging therapeutic regimens demonstrated marked intratumor heterogeneity in the timing and extent of DDR biomarker activation due, in part, to the cell-cycle dependency of DNA damage biomarker expression. CONCLUSIONS: We have demonstrated the clinical utility of this DDR multiplex IFA in preclinical models and clinical specimens following exposure to multiple classes of cytotoxic agents, DNA repair protein inhibitors, and molecularly targeted agents, in both homologous recombination-proficient and -deficient contexts. Levels exceeding 4% nuclear area positive (NAP) γH2AX, 4% NAP pS343-Nbs1, and 5% cells with ≥5 Rad51 nuclear foci indicate a DDR activation response to treatment in human colorectal cancer tissue. Determination of effect-level cutoffs allows for robust interpretation of biomarkers with significant interpatient and intratumor heterogeneity; simultaneous assessment of biomarkers induced at different phases of the DDR guards against the risk of false negatives due to an ill-timed biopsy.

Impact of recreational and medicinal marijuana on surgical patients: A review.

BACKGROUND: As medicinal and recreational marijuana use broadens across the United States, knowledge of its effects on the body will become increasingly important to all health care providers, including surgeons. DATA SOURCES: We performed a literature review of Pubmed for articles discussing the basic science related to cannabinoids, as well as articles regarding cannabinoid medications, and cannabis use in surgical patients. CONCLUSIONS: The primary components in the cannabis plant, tetrahydrocannabinol (THC) and cannabidiol (CBD), have been made available in numerous forms and formulations to treat multiple medical conditions, and recreational access to marijuana is increasing. Of particular importance to the surgeon may be their effects on prolonging intestinal motility, decreasing inflammation, increasing hunger, mitigating pain, and reducing nausea and vomiting. Perioperative use of medicinal or recreational marijuana will become increasingly prevalent, and the surgeon should be aware of the positive and negative effects of these cannabinoids.

Superior mesenteric artery syndrome following sleeve gastrectomy: case report, review of the literature, and video on technique for surgical correction.

Superior mesenteric artery (SMA) syndrome is a rare condition in which the duodenum is compressed between the SMA and aorta. This often occurs following extreme weight loss and has been reported in the bariatric population. We present the first reported case of SMA syndrome following sleeve gastrectomy. The patient underwent laparoscopic duodenojejunostomy and recovered uneventfully. The following is a review of the literature and detailed operative approach in the attached video.

Primary sleeve gastrectomy compared to sleeve gastrectomy as revisional surgery: weight loss and complications at intermediate follow-up.

INTRODUCTION: The laparoscopic adjustable gastric band (LAGB) can be revised to sleeve gastrectomy (LSG) for various reasons. Data are limited on the safety and efficacy of single-stage removal of LAGB and creation of LSG. METHODS: A retrospective review of cases was performed from 2010 to 2013. From the primary LSG group, a control group was matched in a 2:1 ratio. RESULTS: Thirty-two patients underwent single-stage revision from LAGB to LSG, with a control group of 64. The most common indication for revision was insufficient weight loss (62.5%). Operative time for revision and control groups was 134 and 92 min, respectively (p < 0.0001). Hospital stay was 3.22 and 2.59 days, respectively (p = 0.02). Overall, the 30-day complication rate for revision and control patients was 14.71 and 6.25%, respectively (p = 0.20). There were no leaks, one stricture (3.13%) in the revision group, and one reoperation for bleeding in the control group (1.56%). For patients with BMI >30 at surgery, change in BMI at 12 months for revision and control was 8.77 and 11.58, respectively (p = 0.02). CONCLUSION: Single-stage revision can be performed safely, with minimal increases in hospital stay and 30-day complications. Weight loss is greater in those who undergo primary LSG compared to those who undergo LSG as revision.