Outcomes of Six-Dose High-Dose Cytarabine as a Salvage Regimen for Patients with Relapsed/Refractory Acute Myeloid Leukemia

Toxicity and outcome of adults with acute myeloid leukemia receiving consolidation with high-dose cytarabine

INTRODUCTION

High-dose cytarabine is considered standard of care as consolidation chemotherapy in adults with acute myeloid leukemia (AML) who are not eligible for allogeneic hematopoietic cell transplantation, but may be associated with significant toxicity. We evaluated the toxicity associated with high-dose cytarabine given as consolidation in AML patients treated at a Brazilian public hospital.

METHODS

We retrospectively reviewed the charts of all patients with AML treated between 2008 and 2020 who obtained complete remission (CR) after one cycle of induction chemotherapy and received consolidation with at least one cycle of high-dose cytarabine (defined as 3 g/m2 every 12 h days 1, 3 and 5).

RESULTS

Among 61 patients who received induction remission, 32 obtained CR and 28 received at least one cycle of high-dose cytarabine, for a total of 67 cycles (median 2 cycles per patient, range 1 - 4). In 45 cycles (67.2%) the patient was discharged after the end of chemotherapy, with a median of 6 days at home (range 3 - 8). Readmission occurred in 31 of the 45 cycles (68.9%). The most frequent toxicities were febrile neutropenia (56.7%), nausea and vomiting (23.9%), oral mucositis (14.9%) and diarrhea (11.9%). Bacteremia was documented in 13 cycles (34.2%). There were three cases of typhlitis and two of invasive fungal disease (aspergillosis and candidemia). Four patients died (14.3%), with two deaths considered treatment-related (candidemia and typhlitis).

CONCLUSION

In the setting of a Brazilian public hospital, high-dose cytarabine as consolidation therapy is feasible, with manageable toxicity profile.

Healthcare resource utilization and costs during first salvage therapy for relapsed or refractory acute myeloid leukemia in the United States

Real-world US healthcare resource utilization (HRU) and costs during first salvage therapy for relapsed/refractory (R/R) acute myeloid leukemia (AML) are described using IBM MarketScan® data (1/1/2007-6/30/2020). Treatments included high- (HIC) and low-intensity chemotherapy (LIC) alone, and gilteritinib, other FLT3 tyrosine kinase inhibitors (TKIs), and venetoclax with or without chemotherapy. Patients were diagnosed with R/R AML at ≥18 years of age between 1/1/2017-12/31/2019. Patient monthly all-cause HRU and costs were analyzed using a fixed-effects model. Data from 399 patients were analyzed (HIC, n = 104; LIC, n = 133; gilteritinib, n = 14; other FLT3 TKIs, n = 68; venetoclax, n = 80). Inpatient HRU was generally highest with HIC, whereas outpatient HRU was generally highest with LIC and venetoclax. Total all-cause incremental monthly costs appeared to be highest with HIC ($171,982) and similar for LIC ($60,512), gilteritinib ($47,218), other FLT3 TKIs ($43,218), and venetoclax ($77,566). Results highlight HRU and cost differences for R/R AML during first salvage therapy.

JAK-STAT inhibitor as a potential therapeutic opportunity in AML patients resistant to cytarabine and epigenetic therapy

The prognosis of AML is generally poor, with 5-year survival rate of 25%. There has been substantial progress in identification of new therapeutic targets, along with approval of at least three targeted therapies for AML in recent years. Nevertheless, treatment has largely remained unchanged over couple of decades, with ~40% patients not achieving remission. AML is a highly heterogenous disease and there is a need for a preclinical platform to understand the heterogeneity and tumor microenvironment that can guide therapy selection. In this study, we employed an ex vivo tumor explant model to study tumor microenvironment and to select a treatment course for AML patients. Our data reveal dysregulation of DNA methyltransferase (DNMT) and histone deacetylase (HDAC) in a subset of AML patients. Based on this observation, epigenetic modulators azacitidine and panobinostat alone and in combination, were evaluated as treatment regimens in cytarabine refractory tumors. More than 50% of the treated samples showed response to the combination therapy. In order to explore alternate treatment modalities for tumors refractory to these epigenetic modulators, TCGA data analysis was done which revealed increased expression and hypomethylation of IFNGR1/2, suggesting activation of JAK/STAT pathway in AML. This was further interrogated ex vivo, with p-STAT3 expression in patients' samples. Fedratinib, a JAK/STAT inhibitor was evaluated and 78% tumor efficacy response was achieved. Taken together, our data indicate that ex vivo platform derived from patient samples is capable in guiding optimal therapy selection for various classes of drugs including identification of novel targeted therapies.

RNA Targeting in Acute Myeloid Leukemia

Nucleosides and their analogues constitute an essential family of anticancer drugs. DNA has been the presumptive target of the front-line prodrug for acute myeloid leukemia (AML), cytarabine (ara-C), since the 1980s. Here, the biomolecular targeting of ara-C was evaluated in primary white blood cells using the ara-C mimic "AzC" and azide-alkyne "click" reactions. Fluorescent staining and microscopy revealed that metabolic incorporation of AzC into primary white blood cells was unexpectedly enhanced by the DNA polymerase inhibitor aphidicholine. According to RNaseH digestion and pull-down-and-release experiments, AzC was incorporated into short RNA fragments bound to DNA in peripheral blood monocytes (PBMCs) collected from all six healthy human donors tested. Samples from 22 AML patients (French-American-British classes M4 and M5) exhibited much more heterogeneity, with 27% incorporating AzC into RNA and 55% into DNA. The overall survival of AML patients whose samples incorporated AzC into RNA was approximately 3-fold higher as compared to that of the DNA cohort (p ≤ 0.056, χ² = 3.65). These results suggest that the RNA primers of DNA synthesis are clinically favorable targets of ara-C, and that variable incorporation of nucleoside drugs into DNA versus RNA may enable future patient stratification into treatment-specific subgroups.

Economic and Clinical Burden of Relapsed and/or Refractory Active Treatment Episodes in Patients with Acute Myeloid Leukemia (AML) in the USA: A Retrospective Analysis of a Commercial Payer Database

This retrospective study estimated healthcare resource use (HRU), symptoms and toxicities (SxTox), and costs in relapsed/refractory (R/R) patients with acute myeloid leukemia (AML), stratified by hematopoietic stem cell transplantation (HSCT) status. Claims data were used to identify adult patients with AML diagnoses from 1 January 2008 to 31 March 2016 in the USA. Patients were considered R/R if they had an AML relapse ICD-9 code (205.02) or a line of therapy consistent with R/R disease. The final R/R sample (N = 707) included 476 patients with and 231 patients without HSCT. The mean total episode cost (from relapse date to death or end of study period) for all patients was $439,104 (with HSCT $524,595 and without HSCT $263,310). Inpatient visits accounted for the greatest cost component (mean $308,978) followed by intensive care unit stays (mean $221,537), non-clinician (e.g., lab tests) visits (mean $30,909), and outpatient pharmacy utilization (mean $24,640). Patients with HSCT appeared to have longer episodes of care compared with patients without HSCT (16.8 vs 11.1 months), perhaps reflecting longer survival for HSCT patients. Mean number of visits within each category and their associated costs appeared to be higher in patients with HSCT compared with patients without HSCT. Patients with HSCT appeared to experience more SxTox compared with patients without HSCT across all categories. Results of the current study suggest that there is a substantial HRU and cost burden on R/R AML patients in the USA receiving active treatments. More effective therapies with improved tolerability would meet this tremendous unmet need in the R/R AML population.

Funding: Astellas Pharma, Inc.