INADEQUATE IMMUNE RESPONSE TO COVID-19 VACCINES IN THE PRESENCE OF DISEASE-MODIFYING ANTIRHEUMATIC DRUGS (DMARDS)

SESSION TITLE: Issues After COVID-19 Vaccination Case Posters SESSION TYPE: Case Report Posters PRESENTED ON: 10/19/2022 12:45 pm - 01:45 pm INTRODUCTION: Since the onset of the COVID-19 pandemic, vaccines were introduced to mitigate the spread of the virus. Depending on the COVID-19 vaccine, regimens consist of one dose (ie, J&J) or two doses (ie, Pfizer and Moderna) and is followed by a third dose/booster (for immunocompromised/immunocompetent individuals). Here, we present a case of COVID-19 infection in a triple vaccinated patient with concurrent rheumatoid arthritis (RA) receiving disease modifying antirheumatic drugs (DMARDs) who was unable to mount an adequate immune response to the vaccine. CASE PRESENTATION: Patient is a 67 year old male with PMH of RA (on DMARDs) presented to the ED with complaints of shortness of breath. He was on treatment for RA with leflunomide, rituximab and prednisone. He was COVID-19 triple vaccinated. In ED, the patient was found to be hypoxic, saturating at 87% on room air with a respiratory rate of 18. Physical examination was significant for coarse breath sounds bilaterally and remaining vitals were unremarkable. Patient was initially placed on 3 L oxygen via NC but due to persistent hypoxia, was transitioned to high-flow nasal cannula. Further investigations revealed that the patient was COVID-19 positive. He was treated with remdesivir and dexamethasone. His oxygen requirements continued to escalate and he was ultimately intubated. While in the ICU, the patient's hypoxia continued to worsen despite optimal medical and ventilatory management and he subsequently died. DISCUSSION: DMARDs are a group of medications used to slow the progression of rheumatoid arthritis. They work by reducing the immune response of B cells, T cells and cytokines. Our patient was on two commonly prescribed medications for rheumatoid arthritis, leflunomide and rituximab. The former acts by inhibiting the pyrimidine synthesis pathway, thereby decreasing T lymphocyte production and the latter depletes CD-20 positive B cells. While there is limited data on COVID-19 vaccine, it has been established that patients on DMARDs have reduced antibody titres after immunization against influenza and pneumonia vaccinations [1, 2]. A study assessing the effectiveness of a third vaccine dose in patients taking rituximab vs placebo found a significant difference in seroconversion (78.8% vs 18.2%, p=<0.0001) and neutralizing activity (80.0% vs 21.9%, p=<0.0001) [3]. In our case, the patient was on two immunosuppressive drugs which suppressed both the humoral and cell mediated immunity, resulting in an inadequate immune response and subsequently developing COVID. CONCLUSIONS: This case highlights patients on immunosuppressant therapy failing to mount an adequate immune response to the COVID-19 vaccine, warranting more booster doses in patients on DMARDs. Reference #1: Adler S, Krivine A, Weix J et al. Protective effect of A/ H1N1 vaccination in immune-mediated disease–a prospectively controlled vaccination study. Rheumatology 2012;51:695–700. Reference #2: Franca ILA, Ribeiro ACM, Aikawa NE et al. TNF blockers show distinct patterns of immune response to the pandemic influenza A H1N1 vaccine in inflammatory arthritis patients. Rheumatology 2012;51:2091–8. Reference #3: David S, Koray T, Filippo F et al. Efficacy and safety of SARS-CoV-2 revaccination in non-responders with immune-mediated inflammatory disease. http://dx.doi.org/10.1136/annrheumdis-2021-221554 DISCLOSURES: No relevant relationships by Gursharan Kaur No relevant relationships by Aishwarya Krishnaiah No relevant relationships by sandeep mandal

A Broad Antiviral Strategy: Inhibitors of Human DHODH Pave the Way for Host-Targeting Antivirals against Emerging and Re-Emerging Viruses.

New strategies to rapidly develop broad-spectrum antiviral therapies are urgently required for emerging and re-emerging viruses. Host-targeting antivirals (HTAs) that target the universal host factors necessary for viral replication are the most promising approach, with broad-spectrum, foresighted function, and low resistance. We and others recently identified that host dihydroorotate dehydrogenase (DHODH) is one of the universal host factors essential for the replication of many acute-infectious viruses. DHODH is a rate-limiting enzyme catalyzing the fourth step in de novo pyrimidine synthesis. Therefore, it has also been developed as a therapeutic target for many diseases relying on cellular pyrimidine resources, such as cancers, autoimmune diseases, and viral or bacterial infections. Significantly, the successful use of DHODH inhibitors (DHODHi) against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection further supports the application prospects. This review focuses on the advantages of HTAs and the antiviral effects of DHODHi with clinical applications. The multiple functions of DHODHi in inhibiting viral replication, stimulating ISGs expression, and suppressing cytokine storms make DHODHi a potent strategy against viral infection.

Low-Dose Weekly Decitabine and Venetoclax in TP53-Mutated Myeloid Malignancies

Decitabine (Dec) and Azacitidine (Aza) that target DNA methyltransferase 1 (DNMT1) are hypomethylating agents (HMAs) approved to treat acute myeloid leukemia (AML) in combination with Venetoclax (Ven). The combination is also used to treat high-risk myelodysplastic syndromes, especially TP53-mutated (TP53mut) cases in which responses to HMA alone are short-lived. In most patients (pts), however, myelosuppression from treatment leads to frequent Ven duration and/or dose-reductions, and/or cycle delays. An approach to decrease HMA-mediated myelosuppression but maintain S-phase dependent DNMT1-targeting, evaluated in a previous clinical trial (https://doi.org/10.1111/bjh.16281), is to administer noncytotoxic doses/concentrations of Dec (0.2 mg/kg;~5 mg/m 2) by a frequent-distributed schedule of 1X/week. An approach to decrease Ven mediated myelosuppression but maintain cooperation with HMA, shown in pre-clinical studies, is to administer a single-dose prior to HMA. Ven can depolarize mitochondrial membranes;mitochondrial membrane-potential is essential to function of the mitochondrial enzyme DHODH that produces cytidine/deoxycytidine that competes with HMA in cells. Thus, Ven prior to HMA dosing temporarily inhibits de novo pyrimidine synthesis, to counter a major mechanism of resistance to HMA in MDS/AML, without suppressing normal myelopoiesis (https://doi.org/10.1182/blood-2020-143200). We conducted a retrospective analysis of all pts with TP53mut MDS or AML treated with weekly Ven and low-dose subcutaneous Dec at our institution. We analyzed the characteristics of these pts, response to therapy, and outcomes using standard descriptive statistics. Mutational testing was performed using a commercial next-generation sequencing (NGS) panel. Five pts, 3 male and 2 female, with TP53mut MDS or AML were treated with weekly Ven 400 mg on D1 and subcutaneous Dec 0.2 mg/kg on D2, administered weekly in 28 day cycles. Two pts had MDS (1 de novo, 1 treatment related) and 3 pts had AML (1 de novo, 2 secondary from prior MDS). Four pts (80%) received the treatment in frontline, all with poor performance status (PS), and 1 pt (20%) had R/R disease. Median age at diagnosis was 79 years [41-82]. The only young pt had prolonged severe cytopenias after 1 cycle Dec standard dosing during the peak of COVID-19 pandemic so was switched to this regimen. Of the 4 frontline treated pts, 2 pts had high-risk MDS, and 2 pts had adverse risk AML. The R/R pt had high-risk MDS transformed to AML that was refractory to 2 prior lines of therapy: standard Aza/Ven x5 cycles, then standard Vyxeos. Disease cytogenetics were complex in all pts. 60% (3/5) pts had sole TP53mut on NGS, with median variant allelic frequency (VAF) 48% [28-79]. 80% (4/5) pts were transfusion dependent prior to treatment. Median time to initiating therapy was 7 days from initial or refractory diagnosis [3-59] and median follow-up was 7.8 months (mo) [2.9-11.4]. The overall response rate (ORR) was 100%: 4/4 frontline pts had complete remissions (CR), and the 1 R/R pt achieved morphologic leukemia-free state (MLFS). Median time to best response was 2.9 mo. 50% (2/4) pts became transfusion independent. 40% (2/5) pts lost their TP53mut at best response, and another 40% (2/5) pts had significant reductions (83% and 38%) in TP53 mut VAF. The regimen was well tolerated with no pts stopping therapy due to adverse effects (AE). AE included G3/G4 neutropenia (80%), G1 thrombocytopenia (40%), nausea (20%), fatigue (20%), lower extremity edema (20%), pneumonia (60%), and neutropenic fever (20%) with a median of 1 unplanned hospitalization per pt during follow-up. 60% (3/5) pts remain in CR on continued therapy for a median of 7.8 mo [7.2-9.4] thus far. One pt underwent allogeneic stem cell transplantation, however, died 11.4 mo after conditioning due to transplant related mortality. The R/R pt died after being lost to follow-up 2.9 mo after therapy initiation. No pt had measurable relapse during follow-up. Combination weekly Ven with subcutaneous low-dose Dec is well tolerated yielding igh rates of clinical and molecular response in pts with TP53mut MDS/AML. Although small, this case-series extends previous clinical trial proof-of-activity of non-cytotoxic DNMT1-targeting to a high-risk, poor PS, historically chemorefractory patient population. The regimen allowed frequent, sustained exposure to therapy often not possible with standard HMA/Ven regimens. [Formula presented] Disclosures: Shastri: Kymera Therapeutics: Research Funding;Guidepoint: Consultancy;GLC: Consultancy;Onclive: Honoraria. Gritsman: iOnctura: Research Funding. Feldman: Glycomimetics: Current Employment, Current holder of stock options in a privately-held company. Verma: Celgene: Consultancy;Acceleron: Consultancy;Novartis: Consultancy;Stelexis: Consultancy, Current equity holder in publicly-traded company;Eli Lilly: Research Funding;Curis: Research Funding;Medpacto: Research Funding;Incyte: Research Funding;GSK: Research Funding;BMS: Research Funding;Stelexis: Current equity holder in publicly-traded company;Throws Exception: Current equity holder in publicly-traded company. Saunthararajah: EpiDestiny: Consultancy, Current holder of individual stocks in a privately-held company, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties.

Inhibition of De Novo Pyrimidine Synthesis Depletes Acute Myleogenous Leukemia Stem Cells (LSCs) Burden and Triggers Apoptosis and Differentiation Associated with Oxidative Stress

Background: De novo nucleotide synthesis is necessary to meet the enormous demand for nucleotides, other macromolecules associated with acute myeloid leukemia (AML) progression 1, 2, 34. Hence, we hypothesized that targeting de novo nucleotide synthesis would lead to the depletion of the nucleotide pool, pyrimidine starvation and increase oxidative stress preferentially in leukemic cells compared to their non-malignant counterparts, impacting proliferative and differentiation pathways. Emvododstat (PTC299) is an inhibitor of dihydroorotate dehydrogenase (DHODH), a rate-limiting enzyme for de novo pyrimidine nucleotide synthesis that is currently in a clinical trial for the treatment of AML. Objectives: The goals of these studies were to understand the emvododstat-mediated effects on leukemia growth, differentiation and impact on Leukemia Stem Cells(LSCs). Comprehensive analyses of mitochondrial function, metabolic signaling in PI3K/AKT pathways, apoptotic signatures, and DNA damage responses were carried out. The rationale for clinical testing emvododstat was confirmed in an AML-PDX model. Results: Emvododstat treatment in cytarabine-resistant AML cells and primary AML blasts induced apoptosis, differentiation, and reduced proliferation, with corresponding decreased in cell number and increases in annexin V- and CD14-positive cells. Indeed, the inhibition of de novo nucleotide synthesis compromises the dynamic metabolic landscape and mitochondrial function, as indicated by alterations in the oxygen consumption rate (OCR) and mitochondrial ROS/membrane potential and corresponding differentiation, apoptosis, and/or inhibition of proliferation of LSCs. These effects can be reversed by the addition of exogenous uridine and orotate. Further immunoblotting and mass cytometry (CyTOF) analyses demonstrated changes in apoptotic and cell signaling proteins (cleaved PARP, cleaved caspase-3) and DNA damage responses (TP53, γH2AX) and PI3/AKT pathway downregulation in response to emvododstat. Importantly, emvododstat treatment reduced leukemic cell burden in a mouse model of AML PDX ( Complex karyotype, mutation in ASXL1, IDH2, NRAS), decreased levels of leukemia stem cells frequency (1 in 522,460 Vs 1 in 3,623,599 in vehicle vs emvododstat treated mice), and improved survival. The median survival 40 days vs. 30 days, P=0.0002 in primary transplantation and 36 days vs 53.5 days, P=0.005 in secondary transpantation in a PDX mouse model of human AML. This corresponded with a reduction in the bone marrow burden of leukemia and increased expression of differentiation markers in mice treated with emvododstat (Fig. 1). These data demonstrate effect of emvododstat on mitochondrial functions. Conclusion: Inhibition of de novo pyrimidine synthesis triggers differentiation, apoptosis, and depletes LSCs in AML models. Emvododstat is a novel dihydroorotate dehydrogenase inhibitor being tested in a clinical trial for the treatment of myeloid malignancies and COVID-19. Keywords: AML, emvododstat, DHODH, apoptosis, differentiation References: 1 Thomas, D. & Majeti, R. Biology and relevance of human acute myeloid leukemia stem cells. Blood 129, 1577-1585, doi:10.1182/blood-2016-10-696054 (2017). 2 Quek, L. et al. Genetically distinct leukemic stem cells in human CD34- acute myeloid leukemia are arrested at a hemopoietic precursor-like stage. The Journal of experimental medicine 213, 1513-1535, doi:10.1084/jem.20151775 (2016). 3 Villa, E., Ali, E. S., Sahu, U. & Ben-Sahra, I. Cancer Cells Tune the Signaling Pathways to Empower de Novo Synthesis of Nucleotides. Cancers (Basel) 11, doi:10.3390/cancers11050688 (2019). 4 DeBerardinis, R. J. & Chandel, N. S. Fundamentals of cancer metabolism. Sci Adv 2, e1600200, doi:10.1126/sciadv.1600200 (2016). [Formula presented] Disclosures: Weetall: PTC therapeutics: Current Employment. Sheedy: PTC therapeutics: Current Employment. Ray: PTC therapeutics: Current Employment. Andreeff: Karyopharm: Research Funding;AstraZeneca: Research Funding;Oxford Biomedica UK: Research Funding;Aptose: Consultancy;Daiich -Sankyo: Consultancy, Research Funding;Syndax: Consultancy;Breast Cancer Research Foundation: Research Funding;Reata, Aptose, Eutropics, SentiBio;Chimerix, Oncolyze: Current holder of individual stocks in a privately-held company;Novartis, Cancer UK;Leukemia & Lymphoma Society (LLS), German Research Council;NCI-RDCRN (Rare Disease Clin Network), CLL Foundation;Novartis: Membership on an entity's Board of Directors or advisory committees;Senti-Bio: Consultancy;Medicxi: Consultancy;ONO Pharmaceuticals: Research Funding;Amgen: Research Funding;Glycomimetics: Consultancy. Borthakur: ArgenX: Membership on an entity's Board of Directors or advisory committees;Protagonist: Consultancy;Astex: Research Funding;University of Texas MD Anderson Cancer Center: Current Employment;Ryvu: Research Funding;Takeda: Membership on an entity's Board of Directors or advisory committees;Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees;GSK: Consultancy.