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Session: 617. Acute Myeloid Leukemias: Biomarkers, Molecular Markers and Minimal Residual Disease in Diagnosis and Prognosis: Minimal Residual Disease and Therapy Response
Hematology Disease Topics & Pathways:
Research, clinical trials, Acute Myeloid Malignancies, AML, apoptosis, adult, Translational Research, Non-Biological therapies, elderly, Clinical Research, Chemotherapy, Combination therapy, genomics, Diseases, Therapies, Myeloid Malignancies, Biological Processes, Study Population, Human, Minimal Residual Disease
We have previously reported outcomes for patients (pts) receiving venetoclax (VEN) combined with intensive chemotherapy in fit older pts ≥65 years with newly diagnosed AML (Chua et al, JCO 2020). In contrast to younger populations, NPM1(mut) does confer favorable prognosis in older AML populations. Our prior studies indicate that VEN-based therapies in older pts have promising efficacy in NPM1(mut) AML (DiNardo et al, Blood 2020). To characterise this further, we performed a posthoc analysis of the efficacy of single agent VEN and in combination with chemotherapy in NPM1(mut) AML in the CAVEAT study and explored mechanisms of treatment failure using a multi-omic approach.
Methods
NPM1 MRD was performed using RT-qPCR (sensitivity 10-6). Integrated analysis from bulk sequencing (targeted 42-gene NGS, whole exome/genome sequencing (WES/WGS), RNAseq), single cell (sc) proteogenomic and transcriptomic assessments (scDNA plus surface protein, Tapestri MissioBio; scRNAseq, 10x Genomics) were performed. Flow cytometry included analysis of BCL-2, BCL-XL, MCL1 and BFL1 expression.
Results
Of 85 pts enrolled on the CAVEAT study, 20 had NPM1(mut). Median age of NPM1(mut) vs (wt) was 71 vs 70 years. At a median follow-up of 38.6 months, CR/CRi rates and median OS for NPM1(mut) vs (wt) was 85% vs 72% (p=0.37), and 43.9 vs 15.1 months (p=0.04), respectively.
Pts received a 7-day VEN monotherapy pre-phase prior to CAVEAT induction with paired bone marrow (BM) assessments pre- and at day 8 to evaluate VEN sensitivity. NPM1(mut) pts had a greater median relative blast reduction after 7-day VEN at -66% (range -7 to -98%), compared to -37% (range +51 to -94%) for NPM1(wt) (p=0.03).
18/20 NPM1(mut) sub-group pts completed induction and 17 had serial NPM1 MRD assessments. The NPM1(mut) level fell a median of 4.55-log10 following induction, with 6 (35%) pts achieving MRD negative (MRDneg) status. After all consolidation, 12/16 (75%) were MRDneg. 12/12 (100%) pts in long-term follow up remain MRDneg.
We investigated the mechanisms of resistance in the 5/20 pts with NPM1(mut) whose disease was primary refractory (RD; n=1) or had acquired secondary resistance (Fig). Two patients (CAL-045, CAL-021) had shown BM blast reductions of ≥45% during VEN pre-phase. Subsequently, at the time of clinical treatment failure, both were NPM1(mut) MRD negative indicating eradication of the starting NPM1(mut) clone and early evolution of a new NPM1(wt) population as the mechanism of resistance.
Detailed genomic analysis of CAL-045 showed that a TET2/CBL/NPM1(mut) clone was eradicated, with persistence of TET2 and TET2/CBL(mut) clones lacking NPM1(mut) at the time of refractory disease. scRNAseq analysis of these NPM1(wt) clones revealed a pro-inflammatory signature with elevation in BFL1, a pro-survival gene not targeted by VEN (Fig).
In patient CAL-021, NPM1(mut) was also absent with the emergence of nonsense/frameshift BAX variants at relapse as previously described (Moujalled et al, Blood 2022). BAX deficiency is associated with resistance to BH3-mimetics.
Two other cases (CAL-014, CAL-020) showed BM blast reductions of <45% during VEN pre-phase. In CAL-014, the expansion of an NPM1 subclone was associated with FLT3-ITD. WES revealed evolution of FLT3-ITD loss of heterozygosity at relapse. Flow cytometric analysis demonstrated disproportionate upregulation of intracellular MCL-1 (Fig). In case CAL-020, no obvious genetic determinants of resistance were identified at relapse, with persistence of a DNMT3A/KIT/NPM1(mut) clone (VAF~50%). Whole transcriptome analysis revealed skewed expression of a KIT(mut) allele (from 45% to 88%) at relapse, and protein assessment by flow cytometry revealed marked upregulation of BCL-XL (Fig).
Conclusion
VEN in combination with intensive chemotherapy for NPM1(mut) AML pts ≥65 years resulted in rapid and deep responses (NPM1(mut) MRD-negativity) that are associated with prolonged remissions and OS. Mechanisms of treatment failure among pts with NPM1(mut) are diverse and may include kinase-linked upregulation of alternative BCL-2 family pro-survival members or disruption of downstream pro-apoptotic BAX. 
Disclosures: Chua: BMS, Astra Zeneca, AbbVie, Otsuka: Speakers Bureau; AbbVie, Pfizer, Sumitomo Pharma Oncology: Consultancy. Anstee: AbbVie: Patents & Royalties: employee of the Walter and Eliza Hall Institute, which receives milestone and royalty payments related to venetoclax.. Flensburg: WEHI: Patents & Royalties: Employee of the Walter and Eliza Hall Institute, which receives milestone and royalty payments related to venetoclax.. Teh: AbbVie: Patents & Royalties: employee of the Walter and Eliza Hall Institute, which receives milestone and royalty payments related to venetoclax.. Xu: WEHI: Patents & Royalties: Employee of the Walter and Eliza Hall Institute, which receives milestone and royalty payments related to venetoclax.. Fong: AbbVie, Astellas, RACE oncology, Jazz, Pfizer, Otsuka, Servier: Honoraria; AbbVie, Pfizer, Servier: Speakers Bureau. Gray: Servier: Research Funding; AbbVie: Patents & Royalties: Employees of WEHI receive milestone payments in relation to venetoclax. Fleming: Pfizer: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Gilead: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Servier: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; AstraZeneca: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. Roberts: WEHI: Patents & Royalties: Employee of the Walter and Eliza Hall Institute of Medical Research, which receives milestone and royalty payments related to venetoclax. Recipient of share in royalty payments. ; AbbVie: Research Funding. Majewski: WEHI: Patents & Royalties: Employees of WEHI receive milestone payments in relation to venetoclax.. Wei: Beigene: Consultancy, Honoraria; Shoreline: Consultancy; Abbvie: Consultancy, Honoraria, Research Funding, Speakers Bureau; Roche: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; Aculeus: Consultancy; Amgen: Consultancy, Honoraria, Research Funding; BMS: Consultancy, Honoraria, Research Funding, Speakers Bureau; Servier: Consultancy, Honoraria, Patents & Royalties: MCL1 use, Research Funding, Speakers Bureau; Gilead: Consultancy, Honoraria; Walter and Eliza Hall Institute of Medical Research: Patents & Royalties; Syndax: Research Funding; Jazz: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Research Funding; Astra Zeneca: Consultancy, Honoraria, Research Funding; Astellas: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Consultancy, Honoraria, Research Funding, Speakers Bureau. Brown: The Walter and Eliza Hall Institute of Medical Research: Patents & Royalties: Employee of the Walter and Eliza Hall Institute of Medical Research, which receives milestone and royalty payments related to venetoclax..
OffLabel Disclosure: Venetoclax is a BCL-2 inhibitor that is FDA-approved in some indications. This presentation will focus on correlative study results in the CAVEAT trial which combines venetoclax with modified intensive chemotherapy in AML, which is not an approved indication.