Histone deacetylase inhibitors (HDACis) have garnered significant attention over the past decade for their ability to alter gene expression by modulating chromatin structure. By inhibiting HDAC enzymes, these agents promote the accumulation of acetylated histones, resulting in transcriptional activation of tumor suppressor genes and induction of programmed cell death pathways in malignant cells. Abexinostat is distinguished by its pan-HDAC inhibitory activity, targeting multiple HDAC isoforms, which may enhance its antitumor efficacy across various lymphoma subtypes.

In the recently published Phase 1 trial executed between April 2020 and November 2023, twelve Chinese patients diagnosed with relapsed or refractory B cell NHL were enrolled. The cohort comprised individuals with follicular lymphoma (FL), diffuse large B cell lymphoma (DLBCL), and mantle cell lymphoma (MCL). The study’s primary goal was to evaluate safety and pharmacokinetic parameters of escalating oral doses of abexinostat administered twice daily in a regimen described as “one week on, one week off.” This intermittent schedule was designed to maximize antitumor activity while mitigating potential toxicities.

Patients received abexinostat at dose levels of 40 mg, 60 mg, and 80 mg twice daily, separated by a 4-hour interval, over seven days followed by a seven-day drug-free interval. Importantly, a single dose of abexinostat was administered three days prior to the initiation of the continuous dosing period to assess immediate pharmacokinetics and identify any dose-limiting toxicities. This strategic dosing approach enabled careful monitoring of tolerability while capturing pharmacologic data critical for optimizing future dosing regimens.

The safety evaluation revealed a highly tolerable profile of abexinostat across all dose levels. Notably, no dose-limiting toxicities were observed, even at the highest dose of 80 mg twice daily, which was subsequently declared the recommended Phase 2 dose (RP2D). Adverse events were predominantly mild to moderate, with the most common Grade 3 adverse events including thrombocytopenia and hypertriglyceridemia occurring in a minority of patients. These findings suggested that abexinostat could be administered safely at doses likely to produce meaningful biological effects.

Pharmacokinetic analyses underscored the drug’s favorable absorption and elimination characteristics. Median time to maximum plasma concentration (Tmax) ranged from 0.5 to 1.0 hours post-dose, indicating rapid systemic availability. The terminal half-life (T1/2) varied between 2.56 to 8.31 hours, supporting the twice-daily dosing strategy. Furthermore, plasma concentrations demonstrated dose-proportional kinetics, a desirable pharmacological attribute that facilitates predictable exposure-response relationships.

Efficacy signals from this early-phase trial were equally promising. Within the evaluable patient population, the objective response rate (ORR) was 40%, comprising one complete response and three partial responses. Particularly compelling was the 50% ORR observed among follicular lymphoma patients, a group traditionally characterized by chronic disease courses but often limited treatment responsiveness after multiple relapses. Median progression-free survival for follicular lymphoma patients reached 8.38 months, while duration of response extended to 7.82 months, durations encouraging for such a treatment-refractory population.

While overall survival data remain immature given the study’s timeframe, the absence of deaths during the observation period reinforces the favorable risk-benefit profile of abexinostat. The trial’s pioneering status as the first evaluation of this agent in a Chinese NHL population also expands understanding of HDAC inhibitor pharmacology across diverse ethnic groups, addressing an important gap in global oncology research.

The investigators concluded that the “one week on, one week off” oral dosing schedule is a rational approach based on pharmacokinetic observations, balancing steady drug exposure with recovery periods to reduce cumulative toxicity. This intermittent dosage regimen aligns with contemporary trends in targeted cancer therapies that seek to maintain efficacy while optimizing patient quality of life.

Beyond mere tolerability and pharmacokinetics, the demonstration of clear antitumor activity in heavily pretreated patients positions abexinostat as a candidate for further clinical development. Larger Phase 2 and 3 trials are warranted to confirm these early efficacy signals, delineate patient subgroups most likely to benefit, and potentially explore combination strategies with immunotherapies or standard chemotherapy agents.

This study contributes to the evolving landscape of precision oncology, where molecularly targeted agents such as HDAC inhibitors challenge traditional cytotoxic chemotherapy paradigms. In relapsed or refractory lymphomas, where therapeutic resistance diminishes options, new drugs with novel mechanisms of action are critical to improving survival and quality of life.

Moreover, the research underscores the importance of integrating pharmacokinetic assessments early in drug development programs. Understanding how a candidate drug behaves systemically in various patient populations informs safer and more effective dosing protocols, ultimately accelerating the pathway from bench to bedside.

As abexinostat advances through clinical stages, attention will also turn to biomarker identification to predict response and monitor treatment effects. Delineating epigenetic signatures or immune milieu alterations induced by HDAC inhibition could refine patient selection and personalize therapy.

The promising results from this Phase 1 trial offer hope to patients confronting the challenges of relapsed or refractory B cell NHL. In a disease domain in urgent need of innovation, abexinostat’s favorable safety and preliminary efficacy data propel it forward as a potential new weapon in the oncologist’s armamentarium.

Looking ahead, collaborative global efforts and comprehensive clinical investigations remain essential to validate these findings. Success in these endeavors could herald a new chapter in lymphoma treatment, harnessing epigenetic modulation to achieve durable remissions and improve patient outcomes worldwide.

Subject of Research: Abexinostat as a novel pan-histone deacetylase inhibitor in relapsed/refractory B cell non-Hodgkin lymphoma

Article Title: Safety, pharmacokinetics, and efficacy of abexinostat, an novel histone deacetylase inhibitor, in Chinese patients with relapsed/refractory B cell non-Hodgkin lymphoma: a Phase 1 study

Article References: Gui, L., Xie, Z., Qin, Y. et al. Safety, pharmacokinetics, and efficacy of abexinostat, an novel histone deacetylase inhibitor, in Chinese patients with relapsed/refractory B cell non-Hodgkin lymphoma: a Phase 1 study. BMC Cancer 25, 967 (2025). https://doi.org/10.1186/s12885-025-14370-y

Image Credits: Scienmag.com

DOI: https://doi.org/10.1186/s12885-025-14370-y

MDSCs represent a diverse group of immature myeloid cells known primarily for their potent immunosuppressive capabilities. While their role in various cancers has been a subject of increasing research interest, the extent to which they contribute to immune dysregulation in DLBCL has remained elusive until now. The current study systematically investigates how the quantity and function of MDSCs diverge in patients diagnosed with DLBCL compared to healthy individuals, thereby providing critical insights into tumor-induced immune evasion mechanisms.

The research team employed sophisticated flow cytometry techniques to quantify MDSC populations in peripheral blood samples from newly diagnosed DLBCL patients as well as from healthy donors. Beyond mere quantification, they assessed apoptosis and proliferation rates within these myeloid cells, offering a comprehensive view of their cellular dynamics in the context of lymphoma. Such detailed cellular analysis is pivotal, as it facilitates the understanding of how these cells expand or are functionally reprogrammed in malignancy.

One of the study’s striking findings is the elevated expression levels of MDSCs in DLBCL patients, indicating a skewed myelopoiesis that favors immunosuppressive cell expansion. This aberrant increase suggests that the tumor microenvironment may actively promote the development and maintenance of these suppressive cells, thus undermining the host immune response. Previous literature has hinted at similar phenomena in other cancers, but this research underscores the critical relevance within DLBCL specifically.

To explore the functional repercussions of this expansion, the researchers conducted co-culture experiments, pairing isolated MDSCs with DLBCL cell lines and with autologous T cells. These in vitro models allowed an in-depth evaluation of how MDSCs influence both tumor behavior and T cell immune functions in a controlled setting. Notably, DLBCL tumor cells were found to stimulate the growth of MDSCs, highlighting a feedback loop that may perpetuate immune suppression and tumor progression.

Further analysis demonstrated that MDSCs derived from DLBCL patients exhibited a markedly enhanced capacity to inhibit T cell proliferation and activation. This suppression was not merely quantitative but extended to functional parameters, including the secretion of critical cytokines necessary for potent anti-tumor immunity. The dampening of T cell effector functions by MDSCs represents a significant obstacle to effective immune surveillance and antitumor responses in patients.

The researchers also employed RNA transcriptome sequencing to profile gene expression differences between MDSCs from DLBCL patients and those from healthy donors. This molecular characterization revealed distinctive transcriptional signatures suggestive of heightened immunosuppressive programming and metabolic adaptation within DLBCL-MDSCs. Such data open new frontiers for therapeutic targeting by pinpointing key molecular pathways that sustain MDSC-mediated immune evasion.

Importantly, the study established correlations between MDSC abnormalities and several established clinical parameters in DLBCL, including the Ann Arbor staging system, serum lactate dehydrogenase (LDH) levels, and the International Prognostic Index (IPI) score. These associations reinforce the clinical relevance of MDSCs as biomarkers not only for disease severity but also for predicting patient prognosis and potentially guiding treatment strategies.

This research advances the hypothesis that targeting MDSCs therapeutically could recondition the immune landscape in DLBCL, restoring T cell functionality and enhancing responses to immunochemotherapy. Given the current momentum towards immuno-oncology, such insights hold tremendous potential for developing combination regimens that mitigate immune suppression while directly combating tumor cells.

Moreover, the findings propel further inquiry into the mechanistic underpinnings of MDSC proliferation and function in lymphoma, advocating for expanded studies into their metabolic states, epigenetic modifications, and interactions with other immune subsets. This comprehensive understanding will be paramount for translating laboratory discoveries into clinical interventions.

The confirmation that DLBCL tumor cells actively manipulate the immune microenvironment via MDSCs underscores the necessity to reevaluate existing therapeutic frameworks. Immune checkpoint inhibitors and other immunomodulatory agents may be complemented effectively by therapies designed to deplete or reprogram MDSCs, offering a multipronged assault on lymphoma survival mechanisms.

In conclusion, the elucidation of MDSC abnormalities in DLBCL patients represents a significant milestone in hematological oncology research. By unveiling the mechanisms through which these cells suppress T cell activity and contribute to lymphoma progression, the study lays the foundation for novel biomarker development and targeted therapy. The implications extend beyond DLBCL, as a deeper comprehension of MDSCs could influence approaches across various malignancies characterized by immune escape.

Ultimately, these insights beckon a future where precise modulation of the immune microenvironment enhances patient outcomes, transforming diffuse large B-cell lymphoma from a formidable challenge into a more manageable disease. With continued research and clinical translation, MDSC-focused strategies may become integral components of next-generation lymphoma therapies.

Subject of Research: Abnormalities in proportions and functions of myeloid-derived suppressor cells (MDSCs) in peripheral blood of patients with diffuse large B-cell lymphoma (DLBCL).

Article Title: Abnormal proportions and functions of myeloid-derived suppressor cells in peripheral blood of patients with diffuse large B-cell lymphoma

Article References:
Liu, J., Chen, S., Huang, Y. et al. Abnormal proportions and functions of myeloid-derived suppressor cells in peripheral blood of patients with diffuse large B-cell lymphoma. BMC Cancer 25, 771 (2025). https://doi.org/10.1186/s12885-025-14142-8

Image Credits: Scienmag.com

DOI: https://doi.org/10.1186/s12885-025-14142-8