Lack Of Neutropenia Research Articles

Abstract 1088: Advancing non-cytotoxic DNMT1-targeting to treat chemorefractory pancreatic cancer

Abstract The key epigenetic regulator DNA methyltransferase 1 (DNMT1) is a scientifically validated target in p53-null chemorefractory cancers like pancreatic ductal adenocarcinoma (PDAC) since DNMT1-depletion effects cancer cell cycle exits by p53-independent epithelialization. DNMT1 can be depleted by the pyrimidine nucleoside analog pro-drugs decitabine (Dec) or 5-azacytidine (5Aza). However, PDAC clinical trials with Dec/5Aza disappointed. In pre-clinical and clinical analyses, we found resistance was caused by configurations of pyrimidine metabolism in PDAC cells that forestall Dec or 5Aza processing into DNMT1-depleting nucleotide: high expression of cytidine deaminase (CDA) that rapidly catabolizes Dec/5Aza; and suppression of deoxycytidine kinase (DCK) and uridine kinase 2 (UCK2) that rate limit Dec/5Aza pro-drug processing respectively. Accordingly, combination of Dec with a CDA clinical inhibitor, tetrahydrouridine (THU), enabled DNMT1-depletion and PDAC cytoreduction in vitro and in Dec/gemcitabine-refractory PDAC pre-clinical in vivo models. We then conducted a pilot clinical trial in 13 patients with chemorefractory PDAC given oral THU ~10 mg/kg/day combined with decitabine ~0.2 mg/kg/day, for 5 consecutive days, then twice weekly. This Phase 2 was based on several PK/PD studies in human subjects showing potent non-cytotoxic DNMT1-targeting in myeloid cells. Yet again, there were no meaningful clinical responses in the patients. A reason for this was a surprising lack of neutropenia, the most sensitive indicator of systemic DNMT1-targeting. Upon measuring plasma CDA enzyme activity, we found a >10-fold increase in patients with metastatic vs resectable PDAC. Thus, CDA activity is increased not only locally but also systemically in metastatic PDAC, suggesting a need for higher THU doses. We have also observed DCK downregulation, necessary for Dec/gemcitabine uptake and processing, as a cause of PDAC resistance to Dec/gemcitabine. To counter this mechanism, we discovered that 5Aza upregulates DCK as an adaptive response to 5Aza-mediated decrease in dCTP, while Dec upregulates UCK2 (that mediates 5Aza uptake) as an adaptive response to Dec mediated reductions in dTTP. Thus, we alternated Dec with 5Aza in an in vivo model of gemcitabine-resistant PDAC, to exploit their mutual cross-priming, together with THU to inhibit CDA: median vehicle control tumor measurements 972 mm3(range 726-1267.5); median THU-Dec/THU-5Aza 16 mm3 (range 0-87.5); P<0.00001). A non-cytotoxic, epithelial-differentiation based mechanism was confirmed by significant increases in pancreatic epithelial markers while apoptosis markers were unchanged. In sum, metabolism-based resistance to Dec/5Aza can be countered by clinically relevant modifications to treatment, such as alternating doses of THU/Dec and THU/5Aza, for non-cytotoxic p53-independent therapy, a modality distinct from chemoradiation. Citation Format: Rita Tohme, Francis Enane, Caroline Schuerger, Xiaorong Gu, Melissa Fishel, John Pink, Daniel Lindner, Davendra Sohal, Yogen Saunthararajah. Advancing non-cytotoxic DNMT1-targeting to treat chemorefractory pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1088.

Abstract 754: Unique pharmacologic properties of Dolaflexin-based ADCs—a controlled bystander effect

Abstract Antibody-drug conjugates (ADCs) are designed to bind tumor-associated antigens and deliver conjugated cytotoxic payloads to antigen-positive cells. Some ADCs also kill neighboring cells (including antigen-negative cells) by a mechanism referred to as the bystander effect. This effect can be beneficial when the antigen has heterogeneous expression among cells in a solid tumor, but it can also increase off-target toxicity of ADCs. Herein, we report on a unique pharmacologic property of the Dolaflexin platform, which provides a controlled bystander effect that retains the benefits of the bystander effect with respect to antitumor cytotoxicity but reduces the off-target toxicity. The controlled bystander effect, termed “Dolalock,” was achieved through design of a payload, auristatin F-hydroxypropylamide (AF-HPA), that is membrane-permeable and capable of bystander killing but is further catabolized to membrane-impermeable auristatin F (AF). This catabolism of the payload “locks” the highly potent AF in the cell. Using Dolaflexin-based ADCs, we investigated the extent of intracellular AF-HPA and AF release, tumor cell retention and bystander activities in vitro and in vivo. We observed both auristatin species within cells. Co-culture assays with HER2-positive and HER2-negative cells confirmed the cell permeability and bystander-killing capabilities of AF-HPA released from a Dolaflexin-based ADC. Biodistribution studies of Dolaflexin-based ADCs revealed time-dependent concentrations of AF-HPA and AF as well as significant accumulation of AF in xenografted tumor cells, consistent with the Dolalock mechanism. An additional benefit of AF formation was seen in multidrug-resistant transporter studies, which demonstrate that AF, in contrast to AF-HPA, is not a P-glycoprotein 1 (Pgp) substrate. This property may offer additional benefit in Pgp-expressing tumors. In summary, we have shown that the novel AF-HPA payload used in the Dolaflexin platform allows for a controlled bystander effect that likely contributes to the enhanced efficacy and lack of neutropenia we have observed with Dolaflexin-based ADCs. Citation Format: Susan M. Clardy, Alex Yurkovetskiy, Mao Yin, Dmitry Gumerov, Ling Xu, Elena Ter-Ovanesyan, Charlie Bu, Alex Johnson, Marina Protopopova, Qingxiu Zhang, Natalya Bodyak, Marc Damelin, David H. Lee, Donald Bergstrom, Timothy B. Lowinger. Unique pharmacologic properties of Dolaflexin-based ADCs—a controlled bystander effect [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 754.

The role of neutropenia on outcomes of cancer patients with community-acquired pneumonia

Although the presence of neutropenia may predispose cancer patients to develop community-acquired pneumonia, the role of neutropenia on their outcomes has not been investigated. The purpose of the present study was to compare clinical outcomes of cancer community-acquired pneumonia patients with and without neutropenia. Patients with cancer, identified in the Community-Acquired Pneumonia Organization database, were divided into two groups according to the type of cancer and the presence of neutropenia: patients with solid cancer without neutropenia versus those with functional or absolute neutropenia. Among the 3,106 community-acquired pneumonia patients enrolled, 135 had cancer without neutropenia and 75 had cancer with neutropenia. No significant difference was found between patients with and without neutropenia regarding mean time to clinical stability (5.4+/-2.7 versus 4.9+/-2.7 days, respectively), mean length of hospital stay (9.2+/-7.7 versus 9.9+/-9.6 days) and in-hospital mortality (18 versus 15%, respectively). Using a multiple logistic regression model, neutropenia was not associated with mortality in cancer patients when adjusting for significant covariates (odds ratio 1.30). Lack of neutropenia, during the initial evaluation of a cancer community-acquired pneumonia patient, should not be considered an indicator of better clinical outcome.