Pembrolizumab in Patients With Metastatic Breast Cancer With High Tumor Mutational Burden: Results From the Targeted Agent and Profiling Utilization Registry (TAPUR) Study.

PURPOSE: The TAPUR Study is a phase II basket trial that aims to identify signals of antitumor activity of commercially available targeted agents in patients with advanced cancers harboring genomic alterations known to be drug targets. Results in a cohort of patients with metastatic breast cancer (mBC) with high tumor mutational burden (HTMB) treated with pembrolizumab are reported. METHODS: Patients with advanced mBC received standard doses of either 2 mg/kg or 200 mg infusions of pembrolizumab every 3 weeks. Simon's two-stage design was used with a primary study end point of disease control (DC) defined as objective response or stable disease of at least 16 weeks duration. If two or more patients in stage I achieved DC, the cohort would enroll 18 additional patients in stage II. Secondary end points include progression-free survival (PFS), overall survival, and safety. RESULTS: Twenty-eight patients were enrolled from October 2016 to July 2018. All patients' tumors had HTMB ranging from 9 to 37 mutations/megabase. DC and objective response were noted in 37% (95% CI, 21 to 50) and 21% of patients (95% CI, 8 to 41), respectively. Median PFS was 10.6 weeks (95% CI, 7.7 to 21.1); median overall survival was 30.6 weeks (95% CI, 18.3 to 103.3). No relationship was observed between PFS and tumor mutational burden. Five patients experienced ≥ 1 serious adverse event or grade 3 adverse event at least possibly related to pembrolizumab consistent with the product label. CONCLUSION: Pembrolizumab monotherapy has antitumor activity in heavily pretreated patients with mBC characterized by HTMB. Our findings support the recent US Food and Drug Administration approval of pembrolizumab for treatment of patients with unresectable or metastatic solid tumors with HTMB without alternative treatment options.

Antibiotic Korormicin A Kills Bacteria by Producing Reactive Oxygen Species.

Korormicin is an antibiotic produced by some pseudoalteromonads which selectively kills Gram-negative bacteria that express the Na+-pumping NADH:quinone oxidoreductase (Na+-NQR.) We show that although korormicin is an inhibitor of Na+-NQR, the antibiotic action is not a direct result of inhibiting enzyme activity. Instead, perturbation of electron transfer inside the enzyme promotes a reaction between O2 and one or more redox cofactors in the enzyme (likely the flavin adenine dinucleotide [FAD] and 2Fe-2S center), leading to the production of reactive oxygen species (ROS). All Pseudoalteromonas contain the nqr operon in their genomes, including Pseudoalteromonas strain J010, which produces korormicin. We present activity data indicating that this strain expresses an active Na+-NQR and that this enzyme is not susceptible to korormicin inhibition. On the basis of our DNA sequence data, we show that the Na+-NQR of Pseudoalteromonas J010 carries an amino acid substitution (NqrB-G141A; Vibrio cholerae numbering) that in other Na+-NQRs confers resistance against korormicin. This is likely the reason that a functional Na+-NQR is able to exist in a bacterium that produces a compound that typically inhibits this enzyme and causes cell death. Korormicin is an effective antibiotic against such pathogens as Vibrio cholerae, Aliivibrio fischeri, and Pseudomonas aeruginosa but has no effect on Bacteroides fragilis and Bacteroides thetaiotaomicron, microorganisms that are important members of the human intestinal microflora.IMPORTANCE As multidrug antibiotic resistance in pathogenic bacteria continues to rise, there is a critical need for novel antimicrobial agents. An essential requirement for a useful antibiotic is that it selectively targets bacteria without significant effects on the eukaryotic hosts. Korormicin is an excellent candidate in this respect because it targets a unique respiratory enzyme found only in prokaryotes, the Na+-pumping NADH:quinone oxidoreductase (Na+-NQR). Korormicin is synthesized by some species of the marine bacterium Pseudoalteromonas and is a potent and specific inhibitor of Na+-NQR, an enzyme that is essential for the survival and proliferation of many Gram-negative human pathogens, including Vibrio cholerae and Pseudomonas aeruginosa, among others. Here, we identified how korormicin selectively kills these bacteria. The binding of korormicin to Na+-NQR promotes the formation of reactive oxygen species generated by the reaction of the FAD and the 2Fe-2S center cofactors with O2.

Palbociclib in Patients With Pancreatic and Biliary Cancer With CDKN2A Alterations: Results From the Targeted Agent and Profiling Utilization Registry Study.

PURPOSE: The Targeted Agent and Profiling Utilization Registry (TAPUR) Study identifies signals of antitumor activity of commercially available targeted agents in patients with advanced cancers that harbor genomic alterations known as drug targets. In this article, data from two cohorts of patients with pancreatic and biliary cancers with CDKN2A loss or mutation treated with palbociclib are reported. METHODS: Eligible patients age 12 years and older with advanced measurable or evaluable solid tumors are provided treatment according to protocol-specified genomic matching rules. The primary study end point is objective response or stable disease of at least 16 weeks duration. For each cohort, a Simon two-stage design was used with a futility evaluation after 10 patients. Secondary end points include safety, progression-free survival (PFS), and overall survival (OS). RESULTS: Between July 2016 and November 2017, 12 and 10 patients with pancreatic and biliary cancer, respectively, with CDKN2A loss or mutation were treated with palbociclib. Twenty evaluable patients (10 per cohort) were included in the analysis. No patients had objective response or stable disease at 16 weeks, and both cohorts were closed. Two patients, neither with response, were determined to be ineligible. All patients were evaluated for safety, PFS, and OS. A median PFS of 7.2 weeks (90% CI, 4.0 to 8.0 weeks) and median OS of 12.4 weeks (90% CI, 4.7 to 23.1 weeks) were observed in the pancreatic cohort. A median PFS of 7.3 weeks (90% CI, 3.9 to 7.9 weeks) and median OS of 11.1 weeks (90% CI, 5.1 to 14.0 weeks) were observed in the biliary cohort. No unexpected toxicities were observed. CONCLUSION: Palbociclib monotherapy does not have clinical activity in patients with advanced pancreatic or biliary cancers with CDKN2A loss or mutation. Toxicity is similar to reported experience with palbociclib in other tumor types.