Pulse Regimen Research Articles

Dengue-Related Hemophagocytic Lymphohistiocytosis in an Adult: A Case Report and Brief Update

AbstractDengue virus is an arbovirus transmitted through the bite of infected Aedes mosquitoes. Many unusual clinical features are being reported in dengue. Dengue complicated with hemophagocytic lymphohistiocytosis (HLH) is a rare but potentially fatal condition. Here, we report an 18-year-old otherwise healthy female with dengue fever complicated with HLH. The diagnosis was made by fulfilling the clinical and laboratory criteria of HLH. She was managed successfully with a methylprednisolone pulse regimen. Our case highlights the importance of early recognition of complications and prompt treatment for a better outcome.

Intermittent pulses of methylprednisolone with low-dose prednisone attenuate lupus symptoms in B6.MRL-Faslpr/J mice with fewer glucocorticoid side effects

Glucocorticoids (GCs) are potent anti-inflammatory and immunosuppressant medications and remain the cornerstone of systemic lupus erythematosus (SLE) therapy. However, ongoing exposure to GCs has the potential to elicit multiple adverse effects. Considering the irreplaceability of GCs in SLE therapy, it is important to explore the optimal regimen of GCs. Here, we compared the long-term efficacy and safety of pulsed and oral GC therapy in a lupus-prone mouse model. Mice were grouped using a randomized block design. We monitored survival rates, proteinuria, serum autoantibodies, and complement 3 (C3) levels up to 28 weeks of age, and assessed renal damage, bone quality, lipid deposition in the liver and marrow, glucose metabolic parameters, and levels of hormones of the hypothalamic-pituitary-adrenal (HPA) axis. Finally, we explored the mechanisms underlying the superior efficacy of the pulse regimen over oral prednisone regimen. We found that both GC regimens alleviated the poor survival rate, proteinuria, and glomerulonephritis, while also reducing serum autoantibodies and increasing the level of C3. The pulsed GC regimen showed less resistance to insulin, less suppression of the HPA axis, less bone loss, and less bone marrow fat deposition than the oral GC regimen. Additionally, GC-induced leucine zipper (GILZ) was significantly overexpressed in the GC pulse group. These results suggest that the GC pulse regimen ameliorated symptoms in lupus-prone mice, with fewer side effects, which may be related to GILZ overexpression. Our findings offer a potentially promising GC treatment option for SLE.

Psilocybin pulse regimen reduces cluster headache attack frequency in the blinded extension phase of a randomized controlled trial

BackgroundIn a recent randomized, double-blind, placebo-controlled study, we observed a nonsignificant reduction of attack frequency in cluster headache after pulse administration of psilocybin (10 mg/70 kg, 3 doses, 5 days apart each). We carried out a blinded extension phase to consider the safety and efficacy of repeating the pulse regimen. MethodsEligible participants returned to receive a psilocybin pulse at least 6 months after their first round of study participation. Participants kept headache diaries starting two weeks before and continuing through eight weeks after the first drug session. Ten participants completed the extension phase and all ten were included in the final analysis. ResultsIn the three weeks after the start of the pulse, cluster attack frequency was significantly reduced from baseline (18.4 [95% confidence interval 8.4 to 28.4] to 9.8 [4.3 to 15.2] attacks/week; p = 0.013, d’ = 0.97). A reduction of approximately 50% was seen regardless of individual response to psilocybin in the first round. Psilocybin was well-tolerated without any unexpected or serious adverse events. DiscussionThis study shows a significant reduction in cluster attack frequency in a repeat round of pulse psilocybin administration and suggests that prior response may not predict the effect of repeated treatment. To gauge the full potential of psilocybin as a viable medicine in cluster headache, future work should investigate the safety and therapeutic efficacy in larger, more representative samples over a longer time period, including repeating the treatment.Clinical Trials Registration: NCT02981173

Abstract 7274: Optimization of intermittent dosing strategies of KRAS G12C inhibitors in preclinical lung cancer model

Abstract Cysteine-binding targeted drugs AMG-510 and MRTX-849 provide a new therapeutic approach for advanced KRASG12C mutant cancers. However, clinical response has been limited. Responders eventually develop adaptive resistance by gaining additional MAPK pathway mutations, resulting in limited therapeutic benefit. High-dose pulsatile treatment with MAPK pathway inhibitors has been proposed as an alternative strategy to alleviate adaptive resistance while maintaining tumor control. The sensitivity of tumor cells to pan-inhibitors of the MAPK pathway, crucial for proliferation, creates a therapeutic opportunity window for immune cells to restore their function during an intermittent regimen. Congruently, we have previously shown that intermittent pan-MAPK pathway inhibitor treatment delays drug resistance, supports T cell activation, and enhances tumor delay when combined with immunotherapy. In this study, we investigated the effects of continuous and pulsatile KRASG12C inhibition on tumor and immune cells in order to design combinatorial strategies with immune-modulating agents that overcome drug resistance. Our data suggest that a weekly single high-dose regimen of AMG-510 is less effective at achieving tumor control in preclinical mouse models of KRAS mutant lung cancer compared to daily treatments. However, supplementing this pulsatile regimen with lower maintenance doses markedly slows the growth of LLC KRASG12C lung cancer. Flow cytometry analysis revealed that high-dose pulse regimen enhances T cell activation, evidenced by increased expression of TCF-1, Ki67, PD-1, and GITR, along with lower expression of co-inhibitory molecules Lag-3 and Tim-3, 3 days after treatment. In vitro, AMG-510 also improves the antigen presentation of OVA-expressing LLC-KML lung cancer cells via MHC class I and, to a lesser extent, MHC class II. Furthermore, we found that while combinatorial therapy with PD-1 blockade alone does not significantly impact tumor control, the combination with CTLA-4 blockade shows efficacy across pulsatile and continuous AMG-510 dosing cohorts. Overall, our findings suggest that the utilization of intermittent dosing regimens for selective KRASG12C inhibitors is a promising approach for improving clinical responses in lung cancers with KRAS mutations. Future experiments will aim to delineate MAPK pathway behavior in vivo and in vitro under pulsatile and continuous treatment, assess immunogenicity, and further characterize immune changes in the different treatment regimens, with the goal of designing more efficient cancer therapies utilizing selective KRAS inhibitors. Citation Format: Valeria Estrada Navarro, Vincent Panneton, Lauren Dong, Hyejin Choi, Divya Venkatesh, Rachana Maniyar, Isabell Schulze, Jedd D. Wolchok, Taha Merghoub. Optimization of intermittent dosing strategies of KRAS G12C inhibitors in preclinical lung cancer model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7274.

Pulsed dosing and extended daily dosing of oral vancomycin do not facilitate clearance of Clostridioides difficile colonization in mice.

Vancomycin taper and pulse regimens are commonly used to treat recurrent Clostridioides difficile infections, but the mechanism by which these regimens might reduce recurrences is unclear. Here, we used a mouse model to test the hypothesis that pulse dosing of vancomycin after a 10-day treatment course enhances clearance of C. difficile from the intestinal tract. Mice with C. difficile colonization received 10 days of once-daily oral vancomycin followed by 20 days of treatment with saline (controls), daily vancomycin, or pulse dosing of vancomycin every 2 or 3 days. Stool samples were collected to measure the concentration of C. difficile during and after treatment, vancomycin concentrations, and growth of vegetative C. difficile during every 3 days dosing. Pulse dosing of vancomycin was not effective in maintaining suppression of C. difficile (P > 0.05 in comparison to saline controls); growth of vegetative C. difficile occurred between pulse doses when vancomycin decreased to undetectable levels. Daily dosing of vancomycin suppressed C. difficile during treatment, but recurrent colonization occurred after treatment in more than 75% of mice, and by post-treatment day 14, there was no significant difference among the control, pulse dosing, and daily dosing groups (P > 0.05). These findings demonstrate that pulse dosing of vancomycin every 2 or 3 days does not facilitate the clearance of C. difficile spores in mice. Studies are needed to examine the impact of vancomycin taper and pulsed regimens in patients.

Pulse versus non-pulse corticosteroid therapy in patients with acute exacerbation of idiopathic pulmonary fibrosis.

Corticosteroids are commonly used for the treatment of acute exacerbation of idiopathic pulmonary fibrosis (AE-IPF); however, the optimal initial dose of corticosteroids remains uncertain due to a lack of sufficient evidence. We evaluated whether the administration of a pulse dose of corticosteroids resulted in improved survival outcomes compared with conventional non-pulse dose of corticosteroids. We retrospectively analysed 238 patients with AE-IPF treated with corticosteroids at a tertiary referral hospital between January 2013 and December 2021. Based on whether a pulse dose of corticosteroids (methylprednisolone of ≥250 mg/day or equivalent) was administered within 7 days of hospitalization for AE-IPF, the patients were divided into the pulse and non-pulse regimen groups. The survival outcomes were compared between the two groups using multivariable regression and propensity score-matched analyses. Among the 238 patients, 59 patients received pulse dose of corticosteroids, whereas 179 patients received conventional non-pulse dose of corticosteroids. After adjusting for the confounding factors related to the baseline clinical and radiographic severity, compared with the conventional non-pulse regimen, the pulse regimen of corticosteroids did not reduce the risk of mortality at the 3-month (aHR 0.84, 95% CI 0.45-1.38) or 12-month (aHR 0.96, 95% CI 0.60-1.25) follow-ups. Propensity score-matched analysis revealed similar results. The survival outcomes of patients with AE-IPF who received a pulse dose of corticosteroids did not differ from those of patients who received conventional non-pulse dose of corticosteroids. Further prospective studies are required to establish the optimal initial dose of corticosteroids for the treatment of AE-IPF.

Combined Pulsed Radiotherapy (“QUAD SHOT” regimen) with Immune Checkpoint Inhibition (ICI) to Enhance Immune Response for LAHNSCC in Patients Considered Ineligible for Curative Intent Therapy

To utilize pulsed QUAD SHOT as an in-situ vaccine by stimulating the tumor microenvironment (TME) and excluding elective nodal sites, to enhance the immune response with concurrent ICI. Thirty-three patients (20 males and 13 females), with a median age of 81 years, seen at two community hospitals, determined to be ineligible for curative treatment, were treated. All pts received pulsed dose QUAD shot regimen to gross disease (44.4-59.2 Gy) spaced 3 weeks apart with addition of an approved ICI (Pembrolizumab or Cemiplimab). ERT was directed ONLY to Gross Primary + nodal disease. ICI was administered in most pts after the first QUAD shot to enhance immune response. ICI was continued adjuvantly until a > Grade 3 adverse event (AE) or progression of disease (POD). Pts with either advanced cutaneous or mucosal SCC were included (cSCC, mSCC). 39% presented with N1-2 adenopathy, and 24% presented with recurrent disease. PD-L1 status were not routinely obtained. The median number of ICI cycles delivered was 5 (range 2-24). All pts completed at least 3 QUAD shots. Overall LRC for all 33 pts was 69.7%, with a mean follow-up of 11 months (1-39). LRC for 33 pts at 1 and 2 years after the end of radiation were 61.07% and 55.52%, respectively. The percentage of pts free from elective regional recurrences at 1 and 2 years was 87.13% for both cSCC and mSCC groups. Overall, 6 pts (18%) experienced distant failure. Freedom from distant failure at 1 yr after QUAD shot completion by pathology was 100.00% for cSCC and 77.08% for mSCC. DFS for all 33 pts at 1 and 2 yrs were 59.39% and 37.12%, respectively. DFS at 1 year for cSCC was 100% and 53% for mSCC. Median DFS for the mSCC was 13.8 months. Overall survival for all 33 pts was 45.45% with a median OS time of 17.7 months. The 1 and 2 year OS rates were 65% and 33%. Overall toxicity was low and manageable. Gr 3 mucositis occurred in 1 patient and 5 (15%) developed Gr 2 AE's. Gr 3/4 IMAR's were observed in 3 pts and included infusion reaction, colitis, and fatigue/FTT and were discontinued. 4 pts required post QUAD PEG's unrelated to radiation toxicity and due to POD. In elderly, frail, or comorbidly ill patients with LAHNC, the addition of ICI to involved field QUAD shot regimen nearly tripled the median OS rate from prior publications with QUAD shot alone from 5.7 months to 17 months in our series. The low percentage of failure in the elective nodal beds was particularly encouraging based on our hypothesis. This approach represents the next step in an evolution away from conventional RT approaches that engender greater toxicity and warrants further study.

Combined pulsed radiotherapy (QUAD shot regimen) with immune checkpoint inhibition (ICI) to enhance immune response for LAHNSCC in patients considered ineligible for curative intent therapy.

6083 Background: Elderly patients with head and neck cancer (HNC) represent a growing population that would benefit from novel, less toxic approaches. Recent negative trial results adding ICI to chemo-RT for LAHNSCC (Javelin, Keynote 412) suggest that total nodal irradiation may create an immunosuppressive tumor microenvironment (TME), blunting the efficacy of ICI. This study was undertaken to use pulsed QUAD SHOT as an in-situ vaccine by stimulating the TME prior to delivery of ICI, excluding elective nodal sites, to enhance the immune response. Methods: 33 pts (20 males/13 females), with a median age of 81, seen at two community hospitals, ineligible for curative therapy, were treated with pulsed dose QUAD shot regimen to gross disease (44.4-59.2 Gy) spaced 3 weeks apart with addition of an approved ICI (Pembrolizumab or Cemiplimab). ERT was directed ONLY to GTV p+/-n. ICI was administered in most ptsafter the 1st QUAD shot to enhance immune response. ICI was continued adjuvantly until a > Grade 3 adverse event (AE) or progression of disease (POD). Pts with either advanced cutaneous or mucosal SCC were included (cSCC, mSCC). 39% presented with N1-2 adenopathy, and 24% presented with recurrent disease. PD-L1 status were not routinely obtained. Results: The median number of ICI cycles delivered was 5 (range 2-24). All pts completed at least 3 QUAD shots. Overall LRC for all 33 pts was 69.7%, with a mean follow-up of 11 months (1-39). LRC for 33 pts at 1 and 2 years after the end of radiation were 61.07% and 55.52%, respectively. The percentage of pts free from elective regional recurrences at 1 and 2 years was 87.13% for both cSCC and mSCC groups. Six pts (18%) experienced distant failure. Freedom from distant failure at 1 yr after QUAD shot completion by pathology was 100.00% for cSCC and 77.08% for mSCC. DFS for all 33 pts at 1 and 2 yrs were 59.39% and 37.12%, respectively. DFS at 1 year for cSCC was 100% and 53% for mSCC. Median DFS for the mSCC was 13.8 months. Overall survival for all 33 pts was 45.45% with a median OS time of 17.7 months. 1 and 2 year OS rates were 65% and 33%. Overall toxicity was low and manageable. Gr 3 mucositis occurred in 1 patient and 5 (15%) developed Gr 2 AE’s. Gr 3/4 IMAR’s were observed in 3 pts and included infusion reaction, colitis, and fatigue/FTT and were discontinued. 4 pts required post QUAD PEG’s unrelated to radiation toxicity and due to POD. Conclusions: In elderly, frail, or comorbidly ill pts with LAHNC, the addition of ICI to involved field pulsed QUAD shot regimen tripled the median OS rate from prior publications with QUAD shot alone from 5.7 months to 17 months in our series. The low percentage of failure in the elective nodal beds was very encouraging based on our hypothesis. This approach represents the next step in an evolution away from conventional RT approaches that engender greater toxicity and warrants further study.

Pulse versus Non-pulse Steroid Regimens in Patients with Coronavirus Disease 2019:

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The Clinical Efficacy, Safety, and Tolerability of Vancomycin for the Treatment of Recurrent Clostridioides difficile Infection - A Systematic Review.

The aim of this systematic review of randomized clinical trials (RCTs) was to examine the efficacy, safety, and tolerability of vancomycin for treatment of recurrent Clostridioides difficile infection (rCDI). The PubMed database was searched from inception to August 23, 2022. An initial screening was performed followed by a full-text evaluation of the papers. Inclusion criteria were RCTs investigating vancomycin for treatment of rCDI. A total of six studies and 269 patients were included in the review. Three studies used a fixed dose regimen of vancomycin, one study used pulse regimen, one study used a taper-and-pulse regimen, and one study used a taper-and-pulse regimen for the participants with two or more recurrences. The resolution of infection varied from 19% to 58.3% in five of six studies reporting this as an outcome. Four out of six studies reported new episodes of rCDI as an intervention outcome, in those studies 50-63% of participants experienced rCDI. Regarding the safety and tolerability of vancomycin treatment for rCDI, one study described several adverse events regarding gastrointestinal discomfort along with fatigue and skin rash. There were no records of serious adverse events in the included studies. While oral vancomycin is mostly safe and well tolerated in the RCTs reviewed here, the efficacy for treating rCDI varies greatly from 19-58.3%, and 50-63% of participants experienced new episodes of rCDI.

Pulse versus nonpulse steroid regimens in patients with coronavirus disease 2019: A systematic review and meta-analysis.

Systemic steroids are associated with reduced mortality in hypoxic patients with coronavirus disease 2019 (COVID‐19). However, there is no consensus on the doses of steroid therapy in these patients. Several studies showed that pulse dose steroids (PDS) could reduce the progression of COVID‐19 pneumonia. However, data regarding the role of PDS in COVID‐19 is still unclear. Therefore, we performed this meta‐analysis to evaluate the role of PDS in COVID‐19 patients compared to nonpulse steroids (NPDS). Comprehensive literature search of PubMed, Embase, Cochrane Library, and Web of Science databases from inception through February 10, 2022 was performed for all published studies comparing PDS to NPDS therapy to manage hypoxic patients with COVID‐19. Primary outcome was mortality. Secondary outcomes were the need for endotracheal intubation, hospital length of stay (LOS), and adverse events in the form of superimposed infections. A total of 10 observational studies involving 3065 patients (1289 patients received PDS and 1776 received NPDS) were included. The mortality rate was similar between PDS and NPDS groups (risk ratio [RR]: 1.23, 95% confidence interval [CI]: 0.92–1.65, p = 0.16). There were no differences in the need for endotracheal intubation (RR: 0.71, 95%: CI 0.37–1.137, p = 0.31), LOS (mean difference: 1.93 days; 95% CI: −1.46–5.33; p = 0.26), or adverse events (RR: 0.93, 95% CI: 0.56–1.57, p = 0.80) between the two groups. Compared to NPDS, PDS was associated with similar mortality rates, need for endotracheal intubation, LOS, and adverse events. Given the observational nature of the included studies, randomized controlled trials are warranted to validate our findings.

Defining optimal treatment for recurrent Clostridioides difficile infection (OpTION study): A randomized, double-blind comparison of three antibiotic regimens for patients with a first or second recurrence

BackgroundAlthough many large, randomized controlled trials (RCT) have been conducted on antibiotic therapy for patients with primary C. difficile infections (CDI), few RCTs have been performed for patients with recurrent CDI (rCDI). In addition, fecal microbial transplant (FMT) is neither FDA-approved or guideline-recommended for patients with pauci-rCDI (first or second recurrences). Therefore, a rigorous RCT of sufficient size was designed to determine the optimal treatment among three antibiotic regimens in current practice for treatment of pauci-rCDI. MethodsVA Cooperative Studies Program (CSP) #596 is a prospective, double-blind, multi-center clinical trial of veteran patients with pauci-rCDI comparing fidaxomicin (FDX) 200 mg twice daily for 10 days and vancomycin (VAN) 125 mg four times daily for 10 days followed by a 3-week vancomycin taper and pulse (VAN-T/P) regimen to a standard course of VAN 125 mg four times daily for 10 days. The primary endpoint is sustained clinical response at day 59, with sustained response measured as a diarrhea composite outcome (D-COM) that includes symptom resolution during treatment (before day 10) without recurrence of diarrhea or other clinically important outcomes through day 59. DiscussionCSP study 596 is designed to compare three current antibiotic treatments for recurrent CDI that are in clinical practice, but which lack high-quality evidence to support strong guideline recommendations. The design of the study which included a pilot phase initiated at six sites with expansion to 24 sites is described along with protocol modifications based on early trial experience and clinical realities including the COVID-19 pandemic.Trial Registration: This study is registered with clinicaltrials.gov (Identifier: NCT02667418).

Abstract P209: Collaborative crosstalk between two apoptosis pathways drives synergy of dual inhibition of BCL-2/MDM2 in preclinical models of neuroblastoma

Abstract Introduction: The prognosis of patients with neuroblastoma is poor, and novel therapeutic strategies are needed to improve clinical outcomes. Neuroblastoma often exhibits a low TP53 mutation rate and overexpresses MDM2 and BCL-2 genes. Dual targeting of the MDM2-P53 and BCL-2 apoptotic pathways is an attractive treatment strategy (Vernooij et al, Mol Cancer Ther 2021; Dalton et al, Mol Cancer Ther 2021) and is under clinical development using idasanutlin and venetoclax. However, the mechanisms of action (MOAs) of this combination in neuroblastoma are not fully understood. Alrizomadlin (APG-115) is a potent, orally bioactive MDM2 inhibitor. Lisaftoclax (APG-2575) is a novel BCL-2 selective inhibitor. Both agents have shown clinical activity in solid and hematologic malignancies (Tolcher et al, J Clin Oncol 2021:2506; Ailawadhi et al, J Clin Oncol 2021:7502). We investigated the effects of combined alrizomadlin and lisaftoclax treatment in preclinical models of neuroblastoma and examined novel MOAs associated with this combination. Materials and Methods: Antiproliferative activity was measured by CellTiter-Glo luminescent cell viability assay. Apoptosis was evaluated by annexin V/propidium iodide staining and flow cytometry. Meso-Scale Discovery ELISA and western blot analyses characterized the mechanisms of this combination’s synergistic effects. In animal studies, clinically relevant doses of lisaftoclax were employed. A pulsed high-dose regimen of alrizomadlin was used to achieve best efficacy and manage on-target toxicity. Results: In TP53WT neuroblastoma cell lines IMR-32 and SH-SY5Y, the combination of lisaftoclax and alrizomadlin synergistically inhibited proliferation and induced apoptosis, as evidenced by elevations in caspase-3/7, cleaved PARP, and annexin V+ subpopulations. Tumor growth was synergistically inhibited in 3 distinct subcutaneous mouse xenograft tumor models derived from neuroblastoma cell lines or patient tumors. In the cell lines, alrizomadlin treatment upregulated proapoptotic BCL-2 family member expression (NOXA, BAX, and PUMA) and downregulated antiapoptotic BCL-2 family member MCL-1, likely sensitizing cancer cells to lisaftoclax-induced apoptosis. Treatment of these cells with lisaftoclax and alrizomadlin reduced all 3 major BIM-related complexes, thereby increasing free BIM and triggering cellular apoptosis. Lisaftoclax and alrizomadlin downregulated NMYC and its transcription target MDM2, preventing the development of alrizomadlin resistance mediated by a feedback upregulation of MDM2, and inhibition of the MDM2-P53 apoptotic pathway by alrizomadlin primed cancer cells to BCL-2 inhibition. Conclusions: Alrizomadlin synergizes with lisaftoclax to achieve synthetic lethality through a regulated interaction at multiple molecular nodules, and inhibition of BCL-2 apoptotic pathway by lisaftoclax may prevent cancer cells from developing resistance to MDM2-P53 inhibition. These data warrant clinical development of combined alrizomadlin and lisaftoclax treatment in patients with neuroblastoma. Citation Format: Douglas D. Fang, Qiuqiong Tang, Qixin Wang, Yanhui Kong, Na Li, Feng Zhou, Ran Tao, Dajun Yang, Yifan Zhai. Collaborative crosstalk between two apoptosis pathways drives synergy of dual inhibition of BCL-2/MDM2 in preclinical models of neuroblastoma [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr P209.

Abstract P208: Synergistic antitumor activity of lisaftoclax (APG-2575) and alrizomadlin (APG-115) through dual targeting of BCL-2/MDM2-P53 apoptotic pathways in preclinical models of acute myeloid leukemia

Abstract Background: In many hematologic malignancies, BCL-2 is overexpressed and is a viable therapeutic target. In relapsed or refractory acute myeloid leukemia (R/R AML), BCL-2 inhibitor venetoclax as a single agent has limited activity, thereby necessitating combination treatments, some of which are actively under clinical development. In addition, the mutation rate of TP53 is rare in AML, and the frequency of MDM2 overexpression is high, representing an opportunity for pharmacologic intervention of the MDM2-P53 apoptosis pathway. Synergistic effects of MDM2 inhibitor idasanutlin and venetoclax have been reported in preclinical models of TP53 wild-type AML (Pan et al, Cancer Cell 2017). Lisaftoclax (APG-2575) and alrizomadlin (APG-115) are novel BCL-2 and MDM2 inhibitors, respectively. They show unique pharmacological properties as well as clinical activity and tolerable safety profiles in patients with hematologic or solid malignancies (Tolcher et al, J Clin Oncol 2021:2506; Ailawadhi et al, J Clin Oncol 2021:7502). Here, we examined the effects of combined lisaftoclax and alrizomadlin in preclinical models of AML. Materials and Methods: AML cell lines and mouse xenograft models were employed. Antiproliferative activity was measured by CellTiter-Glo luminescent cell viability assay. Apoptosis was evaluated by annexin V/propidium iodide staining and flow cytometry. Meso-Scale Discovery ELISA assay and western blot analyses were used to characterize the mechanisms of the synergistic effects of this combination. In animal studies, clinically relevant doses of lisaftoclax were employed. A pulsed high-dose regimen of alrizomadlin was used to achieve best efficacy and manage on-target toxicity. Results: In TP53 wild-type AML cell lines MOLM-13, MV-4-11, and OCI-AML-3, both single-agent lisaftoclax and alrizomadlin exerted apoptogenic activity. The combination had synergistic apoptogenic and antiproliferative activity. In subcutaneous xenograft models derived from MV-4-11 and OCI-AML-3 cells, the combination substantially inhibited tumor growth relative to the impact observed with either single agent. In a systemic xenograft model derived from MOLM-13 cells, the combination significantly (P < .05) extended the life span of tumor-bearing mice by 135% to 237% compared to that of tumor-bearing mice treated with lisaftoclax or alrizomadlin alone, which resulted in extensions of 4% to 26% and 41% to 95%, respectively. Synergistic anti-leukemic activity was confirmed in a patient-derived systemic AML model. Mechanistically, the combination synergistically downregulated anti-apoptotic proteins MCL-1 and BCL-xL and primed AML cells to apoptosis induced by lisaftoclax. Conclusions: We show a significant synergy of lisaftoclax and alrizomadlin and novel mechanisms associated with the combination of these agents in preclinical models of TP53 wild-type AML. These data support investigation into the clinical outcomes of the combination treatment in patients with TP53 wild-type AML. Citation Format: Douglas D. Fang, Qiuqiong Tang, Qixin Wang, Na Li, Feng Zhou, Guoqin Zhai, Yan Yin, Dajun Yang, Yifan Zhai. Synergistic antitumor activity of lisaftoclax (APG-2575) and alrizomadlin (APG-115) through dual targeting of BCL-2/MDM2-P53 apoptotic pathways in preclinical models of acute myeloid leukemia [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr P208.

Systematic Review and Meta-Analysis: Efficacy of Vancomycin Taper and Pulse Regimens in Clostridioides difficile Infection

ABSTRACT Background Vancomycin is the drug of choice for treating Clostridioides difficile infection (CDI). We compare CDI resolution with vancomycin taper, pulse, and taper-and-pulse regimens. Methods We searched for Medline, Embase, Cochrane, and Scopus through October 9th, 2020. Taper regimen was defined as dose reduction over time; pulse was a regimen less frequent than daily. Studies assessing CDI resolution rates were included. Meta-analyses for resolution rates were performed using weighted proportion ratios (WPR). Results Ten studies with 675 patients treated with vancomycin regimens were included. Resolution rates were 83% (212/266, 95% CI 69–94%, I2 = 85%) for taper-and-pulse, 68% (264/383, 95% CI 57–78%, I2 = 72%) for taper alone, and 54% (11/26 95% CI 0–100%, I2 = 86%) for pulse alone regimens. Taper-and-pulse was superior to taper alone (WPR 83% vs 68%, p < 0.0001) and pulse alone (WPR 83% vs 54%, p < 0.0004), no significant difference between taper alone or pulse alone (WPR 68% vs 54%, p = 0.1). Conclusions Limitations of our analysis are a small number of included studies and heterogeneity. Vancomycin taper-and-pulse seems superior to pulse alone or taper alone for recurrent CDI. A randomized controlled trial comparing vancomycin taper-and-pulse to fidaxomicin and microbiome restoration is needed.

PDT with genetically encoded photosensitizer miniSOG on a tumor spheroid model: A comparative study of continuous-wave and pulsed irradiation

BackgroundTherapeutic effects of PDT depend on many factors, including the amount of singlet oxygen, localization of photosensitizer and irradiation protocol. The present study was aimed to compare the cytotoxic mechanisms of PDT under continuous-wave (CW) and pulsed irradiation using a tumor spheroid model and a genetically encoded photosensitizer miniSOG. Methods1O2 detection in miniSOG and flavin mononucleotide (FMN) solutions was performed. Photobleaching of miniSOG in solution and in HeLa tumor spheroids was analyzed. Tumor spheroid morphology and growth and the cell death mechanisms after PDT in CW and pulsed modes were assessed. ResultsWe found a more rapid 1O2 generation and a higher photobleaching rate in miniSOG solution upon irradiation in pulsed mode compared to CW mode. Photobleaching of miniSOG in tumor spheroids was also higher after irradiation in the pulsed mode. PDT of spheroids in CW mode resulted in a moderate expansion of the necrotic core of tumor spheroids and a slight inhibition of spheroid growth. The pulsed mode was more effective in induction of cell death, including apoptosis, and suppression of spheroid growth. ConclusionsComparison of CW and pulsed irradiation modes in PDT with miniSOG showed more pronounced cytotoxic effects of the pulsed mode. Our results suggest that the pulsed irradiation regimen enables enhanced 1O2 production by photosensitizer and stimulates apoptosis. General significanceOur results provide more insights into the cellular mechanisms of anti-cancer PDT and open the way to improvement of light irradiation protocols.

Commissioning of an ultra-high dose rate pulsed electron beam medical LINAC for FLASH RT preclinical animal experiments and future clinical human protocols.

To present the acceptance and the commissioning, to define the reference dose, and to prepare the reference data for a quality assessment (QA) program of an ultra-high dose rate (UHDR) electron device in order to validate it for preclinical animal FLASH radiotherapy (FLASH RT) experiments and for FLASH RT clinical human protocols. The Mobetron® device was evaluated with electron beams of 9MeV in conventional (CONV) mode and of 6 and 9MeV in UHDR mode (nominal energy). The acceptance was performed according to the acceptance protocol of the company. The commissioning consisted of determining the short- and long-term stability of the device, the measurement of percent depth dose curves (PDDs) and profiles at two different positions (with two different dose per pulse regimen) and for different collimator sizes, and the evaluation of the variability of these parameters when changing the pulse width and pulse repetition frequency. Measurements were performed using a redundant and validated dosimetric strategy with alanine and radiochromic films, as well as Advanced Markus ionization chamber for some measurements. The acceptance tests were all within the tolerances of the company's acceptance protocol. The linearity with pulse width was within 1.5% in all cases. The pulse repetition frequency did not affect the delivered dose more than 2% in all cases but 90Hz, for which the larger difference was 3.8%. The reference dosimetry showed a good agreement within the alanine and films with variations of 2.2% or less. The short-term (resp. long-term) stability was less than 1.0% (resp. 1.8%) and was the same in both CONV and UHDR modes. PDDs, profiles, and reference dosimetry were measured at two positions, providing data for two specific dose rates (about 9Gy/pulse and 3Gy/pulse). Maximal beam size was 4 and 6cm at 90% isodose in the two positions tested. There was no difference between CONV and UHDR mode in the beam characteristics tested. The device is commissioned for FLASH RT preclinical biological experiments as well as FLASH RT clinical human protocols.

Nondermatophyte mould onychomycosis.

Nondermatophyte moulds (NDMs) onychomycosis is often difficult to diagnose as NDMs have been considered contaminants of nails. There are several diagnostic methods used to identify NDMs, however, repeated laboratory isolation is recommended to validate pathogenicity. With NDM and mixed infection (dermatophytes plus NDM) onychomycosis on the rise, accurate clinical diagnosis along with mycological tests is recommended. Systemic antifungal agents such as itraconazole and terbinafine (e.g. pulse regimen: 1 pulse=every day for one week, followed by no treatment for three weeks) have shown efficacy in treating onychomycosis caused by various NDMs such as Aspergillus spp., Fusarium spp., Scopulariopsis brevicaulis, and Onychocola canadensis. Studies investigating topical therapy and devices for NDM onychomycosis are limited. The emergence of antifungal resistance necessitates the incorporation of antifungal susceptibility testing into diagnosis when possible, for the management of recalcitrant infections. Case studies documented in the literature show newer azoles such as posaconazole and voriconazole as sometimes effective in treating resistant NDM onychomycosis. Treatment with broad-spectrum antifungal agents (e.g. itraconazole and efinaconazole) and other combination therapy (oral+oral and/or oral+topical) may be considerations in the management of NDM onychomycosis.

797. Management of Patients with Multiple Clostridioides difficile Infection Recurrences using a Tapered-Pulsed Fidaxomicin Strategy

BackgroundThere is a paucity of data assessing outcomes of alternate fidaxomicin strategies in patients with recurrent Clostridioides difficile infection (rCDI). The objective of our study is to evaluate a tapered-pulsed (T-P) fidaxomicin regimen that was administered immediately following a course of CDI treatment with initial symptom resolution in patients with multiple rCDI.MethodsWe reviewed the characteristics and outcomes of 46 consecutive patients who received T-P fidaxomicin between January 1, 2014-June 30, 2019 in a specialty CDI clinic. The first episode in which fidaxomicin T-P was administered was analyzed. Failure was defined as the persistence of diarrhea and/or the need for additional CDI treatment at any time on T-P fidaxomicin. Sustained clinical cure (SCC) was defined as resolution of diarrhea without recurrence. Recurrence was defined as the return of diarrhea requiring retreatment with CDI therapy after completion of T-P fidaxomicin. Both SCC and recurrence were evaluated at 30 and 90 days after completion of T-P fidaxomicin.ResultsThe mean±SD age of the 46 patients was 63.2±19.9 years, 71.7% were female, and the mean±SD CDI episodes within the past year was 3±1.4 . Most patients (73.9%) had previously failed a vancomycin tapered and/or pulsed regimen. Prior to administering T-P fidaxomicin, a treatment regimen was given to ensure resolution of symptoms. The CDI treatment most commonly used (58.7%) was vancomycin. The T-P fidaxomicin regimen used consisted of 200 mg given once daily for 7 days followed by 200 mg every other day for a median (min-max) duration of 33 (6-120) days. Two patients (4%) failed to respond to T-P fidaxomicin; 34 (74%) and 28 (61%) achieved SCC at 30 and 90 days, respectively. Among the 44 patients that successfully completed the T-P fidaxomicin regimen, recurrence developed in 10 (22.7%) and 16 (36.4%) of patients at 30 and 90 days, respectively, with a median (min-max) time to recurrence of 20 (3-87) days (Figure 1). Four patients with recurrence had received subsequent systemic antibiotics.Figure 1. Course of CDI therapy and follow-up ConclusionA tapered-pulsed fidaxomicin strategy may be effective in patients with multiply rCDI who are refractory to other treatments, including a vancomycin tapered and pulsed regimen.DisclosuresLarry H. Danziger, PharmD, Merck (Speaker’s Bureau)

Sustained Induction of Fetal Hemoglobin by Pulse Butyrate Therapy in Sickle Cell Disease

High levels of fetal hemoglobin (Hb F) protect from many of the complications of sickle cell disease and lead to improved survival. Butyrate and other short chain fatty acids were previously shown to increase Hb F production in erythroid cells in vitro and in animal models in vivo. However, butyrates are also known to inhibit the proliferation of many cell types, including erythroid cells. Experience with the use of butyrate in animal models and in early clinical trials demonstrated that the Hb F response may be lost after prolonged administration of high doses of butyrate. We hypothesized that this loss of response may be a result of the antiproliferative effects of butyrate. We designed a regimen consisting of intermittent or pulse therapy in which butyrate was administered for 4 days followed by 10 to 24 days with no drug exposure. This pulse regimen induced fetal globin gene expression in 9 of 11 patients. The mean Hb F in this group increased from 7.2% to 21.0% (P <.002) after intermittent butyrate therapy for a mean duration of 29.9 weeks. This was associated with a parallel increase in the number of F cells and F reticulocytes. The total hemoglobin levels also increased from a mean of 7.8 g/dL to a mean of 8.8 g/dL (P <.006). The increased levels of Hb F were sustained in all responders, including 1 patient who has been on pulse butyrate therapy for more than 28 months. This regimen, which resulted in a marked and sustained increase in Hb F levels in more than two thirds of the adult sickle cell patients enrolled in this study, was well tolerated without adverse side effects. These encouraging results require confirmation along with an appropriate evaluation of clinical outcomes in a larger number of patients with sickle cell disease.