Phase Ib study of eprenetapopt (APR-246) in combination with pembrolizumab in patients with advanced or metastatic solid tumors.

BACKGROUND: We conducted a phase I, multicenter, open-label, dose-finding, and expansion study to determine the safety and preliminary efficacy of eprenetapopt (APR-246) combined with pembrolizumab in patients with advanced/metastatic solid tumors (ClinicalTrials.gov NCT04383938). PATIENTS AND METHODS: For dose-finding, requirements were non-central nervous system primary solid tumor, intolerant to/progressed after ≥1 line of treatment, and eligible for pembrolizumab; for expansion: (i) gastric/gastroesophageal junction tumor, intolerant to/progressed after first-line treatment, and no prior anti-programmed cell death receptor-1 (PD-1)/programmed death-ligand 1 (PD-L1) therapy; (ii) bladder/urothelial tumor, intolerant to/progressed after first-line cisplatin-based chemotherapy, and no prior anti-PD-1/PD-L1 therapy; (iii) non-small-cell lung cancer (NSCLC) with previous anti-PD-1/PD-L1 therapy. Patients received eprenetapopt 4.5 g/day intravenously (IV) on days 1-4 with pembrolizumab 200 mg IV on day 3 in each 21-day cycle. Primary endpoints were dose-limiting toxicity (DLT), adverse events (AEs), and recommended phase II dose (RP2D) of eprenetapopt. RESULTS: Forty patients were enrolled (median age 66 years; range 27-85) and 37 received eprenetapopt plus pembrolizumab. No DLTs were reported and the RP2D for eprenetapopt in combination was 4.5 g/day IV on days 1-4. The most common eprenetapopt-related AEs were dizziness (35.1%), nausea (32.4%), and vomiting (29.7%). AEs leading to eprenetapopt discontinuation occurred in 2/37 patients (5.4%). In efficacy-assessable patients (n = 29), one achieved complete response (urothelial cancer), two achieved partial responses (NSCLC, urothelial cancer), and six patients had stable disease. CONCLUSIONS: The eprenetapopt plus pembrolizumab combination was well tolerated with an acceptable safety profile and showed clinical activity in patients with solid tumors.

Effects of azacitidine in 93 patients with IDH1/2 mutated acute myeloid leukemia/myelodysplastic syndromes: a French retrospective multicenter study.

Isocitrate dehydrogenase 1 (IDH1) and 2 (IDH2) mutations in Myeloid Neoplams (MNs) exhibit DNA hypermethylation via 2-hydroxyglutarate (2HG) over-production. Clinical impact of azacitidine (AZA) remains inconsistent in IDH1/2-mutated MNs and the potential of serum 2HG as a suitable marker of response to AZA is unknown. To address these questions, we retrospectively analyzed 93 MNs patients (78 AML, 11 MDS, 4 CMML) with IDH1/2 mutations treated with AZA. After a median of 5 cycles of AZA, overall response rate was 28% (including 15% complete remission) and median OS was 12.3 months (significantly shorter in AML compared to MDS/CMML patients). In multivariate analysis of AML patients, DNMT3A mutation was associated with shorter OS while IDH1/2 mutation subtypes had no independent impact. No difference was observed in serum 2HG levels upon AZA treatment between responding and refractory patients suggesting that serum 2HG cannot be used as a surrogate marker of AZA response.

IDH mutations in cancer and progress toward development of targeted therapeutics.

Isocitrate dehydrogenase 1 and 2 (IDH1 and IDH2) are key metabolic enzymes, converting isocitrate to α-ketoglutarate (αKG).IDH1 and IDH2 mutations have been identified in multiple tumor types, including gliomas and myeloid malignancies such as acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS). Here we provide an overview of the function of normal and mutated IDH, discuss the role of IDH mutations in tumorigenesis and progression and review the key clinical considerations when treating IDH-mutated tumors based on emerging clinical data from mutant IDH1/2 inhibitor trials. IDH1 and IDH2 mutations confer neomorphic activity in the mutant protein, resulting in the conversion of αKG to the oncometabolite, D-2-hydroxyglutarate (2-HG). The subsequent accumulation of 2-HG results in epigenetic dysregulation via inhibition of αKG-dependent histone and DNA demethylases, and a block in cellular differentiation. There is growing preclinical and clinical evidence suggesting that IDHmutations are involved in neoplasia. Furthermore, preclinical studies assessing small molecule inhibitors of mutant IDH1/2 enzymes have provided proof of concept that this approach decreases intracellular 2-HG levels, reverses epigenetic dysregulation and induces cellular differentiation. Phase I studies of mutant IDH inhibitors are currently ongoing in patients with IDH-mutant hematologic and solid tumors, with early data in hematologic tumors suggesting a manageable safety profile as well as clinical benefit, with a mechanism of action based on differentiation of malignant cells. Inhibition of mutant IDH shows promise as a treatment approach in hematologic malignancies, with further development ongoing in solid tumors and glioma. The mutant IDH inhibitors may have clinical utility both as single agents and in combination strategies that target additional oncogenic pathways.

Expression of α4ß7 integrin on memory CD8(+) T cells at the presentation of acute intestinal GVHD.

Acute intestinal GVHD remains a major source of morbidity after allogeneic hematopoietic cell transplantation (HCT). α4ß7 integrin is a cell surface molecule that mediates lymphocyte trafficking to intestinal tissue. In this analysis, peripheral blood was collected at the time of presentation of symptoms of acute GVHD and before any treatment. In all, 45 samples were collected and divided into three groups on the basis of subsequent evaluation: intestinal GVHD (n=15), skin GVHD (n=20) and no GVHD (n=10). Two patients developed intestinal GVHD after DLI. The no-GVHD group comprised 10 patients who presented with suspicious symptoms, but evaluation yielded other etiologies. Analysis by flow cytometry showed that intestinal GVHD patients had a significantly higher percentage of α4ß7 integrin-expressing memory CD8(+) T cells (median 7.69%; lower and upper quartiles, 1.06% and 11.64%, respectively) compared with patients with skin GVHD (1.26%; 0.57% and 2.49%) and no GVHD (0.96%; 0.44% and 1.85%), P=0.03. No differences were found in α4ß7 expression in any CD4(+) T-cell subsets or naive CD8(+) T cells. This study adds to the evidence that α4ß7 integrin is involved in lymphocyte trafficking in acute intestinal GVHD.

Preinfusion variables predict the predominant unit in the setting of reduced-intensity double cord blood transplantation.

Double cord blood transplantation (DCBT) may overcome the slow hematopoietic recovery and engraftment failure associated with infusion of a single cord blood unit. In DCBT, only one unit typically contributes to long-term hematopoiesis, but little is known about factors affecting cord predominance. As results from a phase I trial suggested that order of infusion may affect cord predominance, we analyzed the effect of preinfusion variables on chimerism patterns of 38 patients enrolled in the initial study and a subsequent phase II trial. All patients were treated with a reduced-intensity conditioning (RIC) regimen of fludarabine, melphalan and thymoglobulin followed by DCBT. By day 100, 66% of patients had hematopoiesis derived from a single cord blood unit. Higher post-thaw total nucleated cell and CD34+ cell dose were associated with cord predominance and in 68% of patients (P=0.03); the predominant cord blood unit was infused first. Only the post-thaw CD34+ cell dose of the predominant unit predicted time to both neutrophil and platelet engraftment. Although based on a small number of patients, our results identify parameters that may affect cord predominance and engraftment in the setting of DCBT following RIC and suggest possible strategies for selecting infusion order for cord blood units.

Regulation of hematopoietic stem cell growth.

Hematopoietic stem cells (HSC) must balance self-renewal and differentiation to provide sufficient primitive cells to sustain hematopoiesis, while generating more mature cells with specialized capabilities. The enhanced self-renewal capacity of primitive HSCs enables their ability to sustain hematopoiesis throughout decades of life and their ability to repopulate a host when used therapeutically in bone marrow transplantation. However, hematopoietic cell perturbations resulting in unchecked self-renewal participate in leukemogenesis. While mechanisms governing self-renewal are still being uncovered, they are thought to bear relationship to the malignant process in a variety of tumor types and may therefore provide useful therapeutic targets in putative cancer stem cells. This review discusses molecular mechanisms recently defined to participate in HSC governance and highlights features of stem cell interactions with the microenvironment that may help guide therapies directed at HSCs.

Determinants for transformation induced by the Axl receptor tyrosine kinase.

The Axl receptor tyrosine kinase is a transforming oncogene in NIH3T3 cells. In order to define structural requirements of the Axl receptor necessary for transformation we passaged recombinant retroviruses carrying the axl cDNA in NIH3T3 cells, generating randomly mutated axl variants. Using this strategy, we have isolated three axl viral strains (1B1, SV8, and FFa4) that show augmented 3T3 cell transforming capacity associated with elevated p140Axl. Upon sequencing, the 1B1 and SV8 proviruses possessed only silent mutations, making p140Axl overexpression the most likely explanation for their increased transformation activity. However, the characterization of FFa4 revealed a deletion of sequences encoding the carboxy-terminal 45 amino acids leading to the generation of a chimeric transcript comprised of a truncated Axl receptor with a segment of the 3' UTR region. Mutational analysis revealed that the transforming activity of FFa4 was specific to the formation of the chimeric receptor rather than to the carboxyl-terminal truncation. Intriguingly, none of the viral strains were able to transform the murine cell lines NR-6 and 32D despite equivalent expression of surface p140Axl protein. Further analysis showed that Axl's transforming potential is dependent on the host cell type, the presence of a putative pp190 as a facilitator for transformation, and the level of p140Axl expression. Taken together, these results underscore the complexity of Axl biology which is dependent on receptor stoichiometry and the cellular background.

GAS6 induces Axl-mediated chemotaxis of vascular smooth muscle cells.

Atherosclerosis and arterial restenosis are disease processes involving the accumulation of vascular smooth muscle cells following vascular injury. Key events leading to these processes are migration and proliferation of these cells. Here, we demonstrate that GAS6, encoded by the growth arrest-specific gene 6, induces a directed migration (chemotaxis) of both rat and human primary vascular smooth muscle cells while showing only marginal mitogenic potential in human vascular smooth muscle cells. GAS6 stimulation induces Axl autophosphorylation in human vascular smooth muscle cells, indicating that specific GAS6-Axl interactions may be associated with GAS6-directed chemotaxis. To test this hypothesis, vascular smooth muscle cells overexpressing Axl were generated by gene transfer and assessed for their ability to migrate along a GAS6 gradient. These Axl overexpressors exhibited 2-5-fold increased sensitivity to GAS6-induced chemotaxis. Furthermore, vascular smooth muscle cells expressing the kinase dead mutant of Axl or exposure to the soluble Axl extracellular domain showed attenuated GAS6-induced migration. Taken together, these results suggest that GAS6 is a novel chemoattractant that induces Axl-mediated migration of vascular smooth muscle cells. The separation of mitogenesis from migration provided by this study may enhance the molecular dissection of cell migration in vascular damage.