First-in-human Study of AZD5153, A Small-molecule Inhibitor of Bromodomain Protein 4, in Patients with Relapsed/Refractory Malignant Solid Tumors and Lymphoma

AZD5153, a reversible, bivalent inhibitor of the bromodomain and extraterminal family protein BRD4, has preclinical activity in multiple tumors. This first-in-human, phase I study investigated AZD5153 alone or with olaparib in patients with relapsed/refractory solid tumors or lymphoma. Adults with relapsed tumors intolerant of, or refractory to, prior therapies received escalating doses of oral AZD5153 once daily or twice daily continuously (21-day cycles), or AZD5153 once daily/twice daily continuously or intermittently plus olaparib 300 mg twice daily, until disease progression or unacceptable toxicity. Between June 30, 2017 and April 19, 2021, 34 patients received monotherapy and 15 received combination therapy. Dose-limiting toxicities were thrombocytopenia/platelet count decreased (n = 4/n = 2) and diarrhea (n = 1). The recommended phase II doses (RP2D) were AZD5153 30 mg once daily or 15 mg twice daily (monotherapy) and 10 mg once daily (intermittent schedule) with olaparib. With AZD5153 monotherapy, common treatment-emergent adverse events (TEAE) included fatigue (38.2%), thrombocytopenia, and diarrhea (each 32.4%); common grade ≥ 3 TEAEs were thrombocytopenia (14.7%) and anemia (8.8%). With the combination, common TEAEs included nausea (66.7%) and fatigue (53.3%); the most common grade ≥ 3 TEAE was thrombocytopenia (26.7%). AZD5153 had dose-dependent pharmacokinetics, with minimal accumulation, and demonstrated dose-dependent modulation of peripheral biomarkers, including upregulation of HEXIM1. One patient with metastatic pancreatic cancer receiving combination treatment had a partial response lasting 4.2 months. These results show AZD5153 was tolerable as monotherapy and in combination at the RP2Ds; common toxicities were fatigue, hematologic AEs, and gastrointestinal AEs. Strong evidence of peripheral target engagement was observed.

First-in-human study of AZD5153, a small molecule inhibitor of bromodomain protein 4 (BRD4), in patients (pts) with relapsed/refractory (RR) malignant solid tumor and lymphoma: Preliminary data

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Background: BRD4 is a bromodomain and extraterminal (BET) protein that regulates oncogenic programs by modifying gene transcription and additional mechanisms. AZD5153 is a novel, reversible BRD4 inhibitor with bivalent mechanism of action and enhanced antitumor activity in preclinical models. This phase 1, multicenter, dose escalation study (NCT03205176) assesses AZD5153’s safety, pharmacokinetics (PK), and pharmacodynamics (PD). We report here preliminary, unvalidated data from AZD5153 monotherapy in pts with RR solid tumor, including lymphoma. Methods: Adult pts received oral AZD5153 QD/BID to determine the MTD. During dose escalation, a continual reassessment model was used to estimate toxicity and all final decisions were made by the Safety Review Committee. PK and PD were characterized using standard methods. Results: As of 1 Nov 2018, 28 pts (78.6% female, median age 66.5 y) were treated in 7 cohorts: 2 mg QD (3 pts), 5 mg QD (3 pts), 10 mg QD (3 pts), 10 mg BID (5 pts), 15 mg BID (4 pts), 20 mg BID (7 pts), and 30 mg QD (3 pts). Treatment was ongoing in 8 pts at data cut-off. Safety findings showed 50% of pts experienced treatment-related AEs. 25% of pts experienced treatment-related Grade ≥3 AEs, which were thrombocytopenia and fatigue (7.1% each), and anemia, diarrhea, and platelet count decreased (3.6% each). SAEs were observed in 25% of pts; none of the SAEs was attributable to AZD5153 alone. Dose-limiting toxicities of thrombocytopenia (1 pt) and diarrhea with herpetic rash leading to discontinuation (1 pt) occurred at 20 mg BID. 53.6% of pts discontinued due to disease progression. Total median treatment duration was 1.3 mo (range up to 8.9 mos). Dose proportional increase in Cmax and AUC were observed across the dose range tested. Tmax ranged from 0.5 to 3 h and t1/2 was 6 h. Dose-dependent changes in expression of target genes (eg, HEXIM1, HIST2H2BF, CD274, and CCR2) and platelet counts were observed in the peripheral blood. Conclusions: AZD5153 monotherapy is safe and tolerated at doses up to 30 mg QD and 15 mg BID. Linear increase in PK was observed. Additional safety and efficacy updates will be reported at the annual meeting. Clinical trial information: NCT03205176.

Ectoenzymes of the kidney microvillar membrane. Affinity purification, characterization and localization of the phospholipase C-solubilized form of renal dipeptidase

Renal dipeptidase (EC 3.4.13.11) was solubilized from pig kidney microvillar membranes with bacterial phosphatidylinositol-specific phospholipase C and then purified by affinity chromatography on cilastatin-Sepharose. The enzyme was apparently homogeneous on SDS/polyacrylamide-gel electrophoresis with an Mr of 47,000. Immunohistochemical analysis of the distribution of the dipeptidase showed it to be concentrated in the brush-border region of the proximal tubules in close association with endopeptidase-24.11) (EC 3.4.24.11). The purified dipeptidase was shown to contain 1 mol of inositol/mol and to possess the cross-reacting determinant characteristic of the glycosyl-phosphatidylinositol membrane-anchoring domain. The glycoprotein nature of renal dipeptidase was confirmed by chemical and enzymic deglycosylation. These results establish renal dipeptidase as a glycosyl-phosphatidylinositol-anchored ectoenzyme of the microvillar membrane.