BCR::ABL1 Kinase N-lobe Mutants Confer Moderate to High Degrees of Resistance to Asciminib.

Secondary kinase domain mutations in BCR::ABL1 represent the most common cause of resistance to tyrosine kinase inhibitor (TKI) therapy in chronic myeloid leukemia patients. The first five approved BCR::ABL1 TKIs target the ATP-binding pocket. Mutations confer resistance to these ATP-competitive TKIs and those approved for other malignancies by decreasing TKI affinity and/or increasing ATP affinity. Asciminib, the first highly active allosteric TKI approved for any malignancy, targets an allosteric regulatory pocket in the BCR::ABL1 kinase C-lobe. As a non-ATP-competitive inhibitor, the activity of asciminib is predicted to be impervious to increases in ATP affinity. Here we report several known mutations that confer resistance to ATP-competitive TKIs in the BCR::ABL1 kinase N-lobe that are distant from the asciminib binding pocket yet unexpectedly confer in vitro resistance to asciminib. Among these is BCR::ABL1 M244V, which confers clinical resistance even to escalated asciminib doses. We demonstrate that BCR::ABL1 M244V does not impair asciminib binding, thereby invoking a novel mechanism of resistance. Molecular dynamics simulations of the M244V substitution implicate stabilization of an active kinase conformation through impact on the -C helix as a mechanism of resistance. These N-lobe mutations may compromise the clinical activity of ongoing combination studies of asciminib with ATP-competitive TKIs.

Low-Dose Linezolid for Treatment of Patients With Multidrug-Resistant Tuberculosis.

Background: Linezolid has been prioritized for treating multidrug-resistant tuberculosis (MDR TB), but toxicity limits its use. We report treatment outcomes for MDR TB patients in California who received standard-dose linezolid vs those who switched to low-dose. Methods: We include culture-positive MDR TB cases treated with linezolid and receiving California MDR TB Service consultation during 2009-2016. Demographic, clinical, and laboratory data are analyzed using univariate analysis to compare patients who received linezolid of different dosing strategies. Analysis end points are linezolid treatment duration (measure of tolerability), treatment success (completion or cure), and adverse events (AEs). Results: Sixty-nine of 194 (36%) MDR TB patients met inclusion criteria. While all patients began linezolid treatment at 600 mg daily, 39 (57%) continued at this dosage (standard-dose), and 30 (43%) switched to 300 mg daily (29%) or intermittent dosing (14%) (low dose). Patients on standard-dose linezolid were treated for 240 days, compared with 535 for those on low-dose (P < .0001). Sixty-three patients (91%) achieved treatment success, 2 (2.9%) died, 1 (1.5%) failed treatment, 1 (1.5%) stopped treatment due to side effects, and 2 (2.9%) were lost or moved. Treatment success was higher (P = .03) in the low-dose group. Sixty-two patients experienced ≥1 hematologic (71%) or neurologic (65%) AE. Those on low-dose linezolid experienced significantly (P = .03) fewer AEs per linezolid-month after switching (0.32 vs 0.10). Conclusions: Patients who switched to low dose tolerated linezolid longer with better treatment outcomes and fewer recurring AEs.

Macrophages and Their Organ Locations Shape Each Other in Development and Homeostasis - A Drosophila Perspective.

Across the animal kingdom, macrophages are known for their functions in innate immunity, but they also play key roles in development and homeostasis. Recent insights from single cell profiling and other approaches in the invertebrate model organism Drosophila melanogaster reveal substantial diversity among Drosophila macrophages (plasmatocytes). Together with vertebrate studies that show genuine expression signatures of macrophages based on their organ microenvironments, it is expected that Drosophila macrophage functional diversity is shaped by their anatomical locations and systemic conditions. In vivo evidence for diverse macrophage functions has already been well established by Drosophila genetics: Drosophila macrophages play key roles in various aspects of development and organogenesis, including embryogenesis and development of the nervous, digestive, and reproductive systems. Macrophages further maintain homeostasis in various organ systems and promote regeneration following organ damage and injury. The interdependence and interplay of tissues and their local macrophage populations in Drosophila have implications for understanding principles of organ development and homeostasis in a wide range of species.

Pediatric tuberculosis consultations across 5 CDC regional tuberculosis training and medical consultation Centers.

BACKGROUND: The U.S. Centers for Disease Control and Prevention (CDC) funds five Regional Tuberculosis Training and Medical Consultation Centers (RTMCCs) that provide training and consultation for tuberculosis (TB) control and management. RTMCC utilization for assistance with diagnosis and management of TB in children has not been described. We analyzed pediatric TB consultations performed across all RTMCCs in terms of question type, provider type, and setting. METHODS: The CDC medical consultation database was queried for consultations regarding patients ≤ 18 years provided between 1/1/13-4/22/15 by all RTMCCs (Curry International TB Center, Heartland National TB Center, Mayo Clinic Center for TB, New Jersey Medical School Global TB Institute, Southeastern National TB Center). Each query was categorized into multiple subject areas based on provider type, setting, consultation topic, and patient age. RESULTS: The 5 RTMCCs received 1164 pediatric consultation requests, representing approximately 20% of all consultations performed by the centers during the study period. Providers requesting consults were primarily physicians (46.3%) or nurses (45.0%). The majority of pediatric consult requests were from state and local public health departments (679, 58.3%) followed by hospital providers (199, 17.1%); fewer requests came from clinicians in private practice (84, 7.2%) or academic institutions (40, 3.4%). Consults addressed 14 different topics, most commonly management of children with TB disease (19.1%), latent TB infection (LTBI) (18.2%), diagnosis or laboratory testing (18.7%), and pharmacology (9.2%). DISCUSSION: Pediatric consultations accounted for approximately 20% of all consultations performed by RTMCCs during the study period. RTMCCs were utilized primarily by public health departments regarding management of TB disease, LTBI, and diagnosis or laboratory testing. The relative underutilization of the RTMCCs by clinicians in non-public health settings, who often manage children with TB exposure or infection, warrants further study. As US TB case rates decline and providers become less experienced with childhood TB, medical consultation support may become increasingly important.