A Randomized, Phase III Trial to Evaluate Rucaparib Monotherapy as Maintenance Treatment in Patients With Newly Diagnosed Ovarian Cancer (ATHENA-MONO/GOG-3020/ENGOT-ov45).

PURPOSE: ATHENA (ClinicalTrials.gov identifier: NCT03522246) was designed to evaluate rucaparib first-line maintenance treatment in a broad patient population, including those without BRCA1 or BRCA2 (BRCA) mutations or other evidence of homologous recombination deficiency (HRD), or high-risk clinical characteristics such as residual disease. We report the results from the ATHENA-MONO comparison of rucaparib versus placebo. METHODS: Patients with stage III-IV high-grade ovarian cancer undergoing surgical cytoreduction (R0/complete resection permitted) and responding to first-line platinum-doublet chemotherapy were randomly assigned 4:1 to oral rucaparib 600 mg twice a day or placebo. Stratification factors were HRD test status, residual disease after chemotherapy, and timing of surgery. The primary end point of investigator-assessed progression-free survival was assessed in a step-down procedure, first in the HRD population (BRCA-mutant or BRCA wild-type/loss of heterozygosity high tumor), and then in the intent-to-treat population. RESULTS: As of March 23, 2022 (data cutoff), 427 and 111 patients were randomly assigned to rucaparib or placebo, respectively (HRD population: 185 v 49). Median progression-free survival (95% CI) was 28.7 months (23.0 to not reached) with rucaparib versus 11.3 months (9.1 to 22.1) with placebo in the HRD population (log-rank P = .0004; hazard ratio [HR], 0.47; 95% CI, 0.31 to 0.72); 20.2 months (15.2 to 24.7) versus 9.2 months (8.3 to 12.2) in the intent-to-treat population (log-rank P < .0001; HR, 0.52; 95% CI, 0.40 to 0.68); and 12.1 months (11.1 to 17.7) versus 9.1 months (4.0 to 12.2) in the HRD-negative population (HR, 0.65; 95% CI, 0.45 to 0.95). The most common grade ≥ 3 treatment-emergent adverse events were anemia (rucaparib, 28.7% v placebo, 0%) and neutropenia (14.6% v 0.9%). CONCLUSION: Rucaparib monotherapy is effective as first-line maintenance, conferring significant benefit versus placebo in patients with advanced ovarian cancer with and without HRD.

The comparative analysis of the properties and structures of purine nucleoside phosphorylases from thermophilic bacterium Thermus thermophilus HB27.

Two recombinant purine nucleoside phosphorylases from thermophilic bacterium Thermus thermophilus HB27 encoded by genes TT_C1070 (TthPNPI) and TT_C0194 (TthPNPII) were purified and characterized. The comparative analysis of their sequences, molecular weight, enzymes specificity and kinetics of the catalyzed reaction were realized. As a result, it was determined that the TthPNPI is specific to guanosine while the TthPNPII to adenosine. According to the results of the size exclusion chromatography and SAXS study both enzymes are hexameric molecules. Based on the sequence alignment with homologous purine nucleoside phosphorylases (PNPs), Asn was identified as a purine base recognizing residue in the active site of TthPNPI and Asp in TthPNPII. The three-dimensional structure of TthPNPII was solved at 2.5 Å resolution by molecular replacement method using crystals grown in microgravity. Position of phosphate in the active site cavity is located. The possible arrangement of adenosine and guanosine in TthPNPII active site cavity is considered using superposition with the structures of homologous trimeric and hexameric PNPs complexed with corresponding substrates. The peculiarities of oligomeric structure of TthPNPII in comparison with homologous PNPs are described. It is shown that two trimeric molecules of TthPNPII in the asymmetric part of the unit cell are connected by three two-fold axis into a hexamer with 32-point symmetry. This type of hexameric structure of PNP is found for the first time. The interface area between the subunits in trimeric molecule and between the trimers in TthPNPII hexamer is described.Communicated by Ramaswamy H. Sarma.

Multi-Enzymatic Cascades in the Synthesis of Modified Nucleosides: Comparison of the Thermophilic and Mesophilic Pathways.

A comparative study of the possibilities of using ribokinase → phosphopentomutase → nucleoside phosphorylase cascades in the synthesis of modified nucleosides was carried out. Recombinant phosphopentomutase from Thermus thermophilus HB27 was obtained for the first time: a strain producing a soluble form of the enzyme was created, and a method for its isolation and chromatographic purification was developed. It was shown that cascade syntheses of modified nucleosides can be carried out both by the mesophilic and thermophilic routes from D-pentoses: ribose, 2-deoxyribose, arabinose, xylose, and 2-deoxy-2-fluoroarabinose. The efficiency of 2-chloradenine nucleoside synthesis decreases in the following order: Rib (92), dRib (74), Ara (66), F-Ara (8), and Xyl (2%) in 30 min for mesophilic enzymes. For thermophilic enzymes: Rib (76), dRib (62), Ara (32), F-Ara (<1), and Xyl (2%) in 30 min. Upon incubation of the reaction mixtures for a day, the amounts of 2-chloroadenine riboside (thermophilic cascade), 2-deoxyribosides (both cascades), and arabinoside (mesophilic cascade) decreased roughly by half. The conversion of the base to 2-fluoroarabinosides and xylosides continued to increase in both cases and reached 20-40%. Four nucleosides were quantitatively produced by a cascade of enzymes from D-ribose and D-arabinose. The ribosides of 8-azaguanine (thermophilic cascade) and allopurinol (mesophilic cascade) were synthesized. For the first time, D-arabinosides of 2-chloro-6-methoxypurine and 2-fluoro-6-methoxypurine were synthesized using the mesophilic cascade. Despite the relatively small difference in temperatures when performing the cascade reactions (50 and 80 °C), the rate of product formation in the reactions with Escherichia coli enzymes was significantly higher. E. coli enzymes also provided a higher content of the target products in the reaction mixture. Therefore, they are more appropriate for use in the polyenzymatic synthesis of modified nucleosides.

Second-line lenvatinib in patients with recurrent endometrial cancer.

OBJECTIVE: This study assessed the efficacy of lenvatinib, a multitargeted tyrosine kinase inhibitor, as second-line therapy in patients with unresectable endometrial cancer. The primary end point was the objective response rate (ORR) as assessed by independent radiologic review (IRR). Secondary end points included median progression-free survival (PFS), overall survival (OS), and clinical benefit rate. Exploratory end points examined the association of baseline levels of plasma biomarkers (50 circulating cytokine and/or angiogenic factors measured by immunoassays) with efficacy outcomes. METHODS: An international, open-label, single-arm, multicenter, phase 2 trial was conducted. Eligible patients had histologically confirmed unresectable endometrial cancer that relapsed after 1 prior systemic platinum-based chemotherapy. Patients received once-daily oral lenvatinib 24 mg in a 28-day dosing cycle. RESULTS: There were 133 patients in the study. By IRR, 19 patients had a confirmed objective response for an ORR of 14.3% (95% CI: 8.8-21.4). Durable stable disease (≥23 weeks) was observed in 31 patients (23.3%) and the clinical benefit rate was 37.6% (95% CI: 29.3-46.4). Median PFS was 5.6 months (95% CI: 3.7-6.3), and median OS was 10.6 months (95% CI: 8.9-14.9). The most common (any grade) treatment-related adverse events were fatigue/asthenia (48%), hypertension (49%), nausea/vomiting (32%), decreased appetite (32%), and diarrhea (31%). Lower baseline levels of angiopoietin-2 were associated with longer PFS, OS, and a higher ORR. CONCLUSIONS: Patients with recurrent endometrial cancer treated with second-line lenvatinib experienced modest antitumor activity and treatment was generally well tolerated, with a safety profile consistent with previous studies.

Crystal structure of recombinant phosphoribosylpyrophosphate synthetase 2 from Thermus thermophilus HB27 complexed with ADP and sulfate ions.

Phosphoribosylpyrophosphate synthetase (PRPPS) from the thermophilic bacterial strain Thermus thermophilus HB27 catalyzes the synthesis of phosphoribosylpyrophosphate from ribose 5-phosphate and ATP, and belongs to the class I PRPPSs. The three-dimensional structure of the recombinant enzyme was solved at 2.2 Šresolution using crystals grown in microgravity from protein solution containing ATP, magnesium and sulfate ions. An ADP molecule was located in the active site of each subunit of the hexameric enzyme molecule and sulfate ions were located in both the active and allosteric sites. It was found that the catalytic loop that restricts the active-site area and is usually missing from the electron-density map of class I PRPPSs adopts different conformations in three independent subunits in T. thermophilus PRPPS. A closed conformation of the active site was found in one of subunits where the highly ordered catalytic ß-hairpin delivers the Lys and Arg residues that are essential for activity directly to the ADP molecule, which occupies the ATP-binding site. A comparison of the conformations of the catalytic loop in the three independent subunits reveals a possible mode of transition from the open to the closed state of the active site during the course of the catalyzed reaction.