ASTX029, a Novel Dual-mechanism ERK Inhibitor, Modulates Both the Phosphorylation and Catalytic Activity of ERK.

The MAPK signaling pathway is commonly upregulated in human cancers. As the primary downstream effector of the MAPK pathway, ERK is an attractive therapeutic target for the treatment of MAPK-activated cancers and for overcoming resistance to upstream inhibition. ASTX029 is a highly potent and selective dual-mechanism ERK inhibitor, discovered using fragment-based drug design. Because of its distinctive ERK-binding mode, ASTX029 inhibits both ERK catalytic activity and the phosphorylation of ERK itself by MEK, despite not directly inhibiting MEK activity. This dual mechanism was demonstrated in cell-free systems, as well as cell lines and xenograft tumor tissue, where the phosphorylation of both ERK and its substrate, ribosomal S6 kinase (RSK), were modulated on treatment with ASTX029. Markers of sensitivity were highlighted in a large cell panel, where ASTX029 preferentially inhibited the proliferation of MAPK-activated cell lines, including those with BRAF or RAS mutations. In vivo, significant antitumor activity was observed in MAPK-activated tumor xenograft models following oral treatment. ASTX029 also demonstrated activity in both in vitro and in vivo models of acquired resistance to MAPK pathway inhibitors. Overall, these findings highlight the therapeutic potential of a dual-mechanism ERK inhibitor such as ASTX029 for the treatment of MAPK-activated cancers, including those which have acquired resistance to inhibitors of upstream components of the MAPK pathway. ASTX029 is currently being evaluated in a first in human phase I-II clinical trial in patients with advanced solid tumors (NCT03520075).

Comparative Diagnostic Performance of the Granulocyte and Neutrophil Counts.

OBJECTIVES: Use of point-of-care testing is increasing, however many haematology analysers can only determine granulocyte count without further differentiation into neutrophils, eosinophils and basophils. Since the diagnosis of life-threatening neutropenia in cancer patients requires a distinct neutrophil count, this study aimed to determine the comparative performance between the neutrophil and granulocyte count. DESIGN AND METHODS: A database of 508 646 venous full blood count results measured on a laboratory reference analyser was mined from a large oncology unit. The relationship between granulocyte and neutrophil counts was assessed. Multinomial logistic regression was used to classify results into neutropenia grades using an equivalent granulocyte count. RESULTS: Granulocyte to neutrophil count correlation was 0.997. The accuracy for classification into neutropenia grades using the derived equivalent granulocyte count ranges was 96.4%. Identification of results with a neutrophil count <1.5×109 cells/L using an equivalent granulocyte count of <1.69×109 cells/L resulted in sensitivity, specificity, positive and negative predictive values of 98.0%, 99.5%, 97.8% and 99.5%, respectively. CONCLUSIONS: These results describe the relationship between granulocyte and neutrophil counts, measured on a laboratory analyser, in a large population of patients with malignancies and receiving anti-cancer therapies. However, this relationship must be established using a point of care testing system with a three-part differential count before considering the possibility that a granulocyte count can guide clinical decisions in the absence of a definitive neutrophil count, to reduce the frequency and severity of neutropenic complications in patients receiving cancer treatments.