New Research Points to HDAC3 Inhibition as a Potential Game-Changing Treatment for Specific Lymphoma Subtypes

By Sucharita Mistry, PhD

B-cell lymphomas such as diffuse large B-cell lymphoma (DLBCL) and follicular lymphoma (FL) are blood cancers of the immune cells. A vast majority of B-cell lymphomas typically display a high frequency of genetic alterations. Since lymphomas show remarkable genetic diversity, a big challenge for scientists is not only to determine which genes are mutated in these diseases, but also to identify “actionable” genetic alterations that can respond to targeted therapies.

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“Discovering how different mutations are involved in causing the disease is a major key to advancing novel mechanism-based precision therapies and immunotherapies for lymphomas, with potentially less toxic side-effects,” says Dr. Ari Melnick, a world-renowned physician-scientist at Weill Cornell Medicine.

Dr. Melnick led groundbreaking research that defines the genetic underpinnings of CREBBP mutation in lymphomas, paving the way for new therapeutic avenues. The findings of this study were recently published in Cancer Discovery.

The CREBBP gene encodes a kind of histone acetyltransferase (HAT), an enzyme that introduces small chemical tags called acetyl groups on histones, which are the major structural proteins of chromosomes. The chemical modifications on histones are termed as epigenetic changes, and they determine whether genes are turned on or off. The CREBBP gene, which is an epigenetic modifier, is frequently mutated in DLBCL and FL.

The Melnick research team, in collaboration with scientists at the MD Anderson Cancer Center, characterized the functional consequences of CREBBP mutation in lymphomas. Using a powerful CRISPR gene-editing technology, the researchers engineered lymphoma cell lines that differed only in the CREBBP mutation status. The research team discovered two different types of CREBBP mutations that either truncate the protein or inactivate the HAT domain, the latter associated with poor clinical outcomes.

This study showed that CREBBP mutation disrupts key biological pathways resulting in abnormal silencing of tumor-suppressive and antigen-presenting pathway genes. This disruption allows lymphoma cells to hide from the immune system so that they cannot be recognized and attacked by the T-cells that play an essential role in the body’s immune response.

More importantly, the malfunction in immune surveillance was restored by an HDAC3 inhibitor, a drug that specifically reverses the histone acetylation defect caused by CREBBP mutation. Notably, selective inhibition of HDAC3 reversed the epigenetic abnormalities, halted lymphoma growth and induced the expression of major histocompatibility (MHC) class II protein, enabling the T cells of the immune system to recognize and kill lymphoma cells. The research team also demonstrated that combination of an HDAC3 inhibitor with an immune checkpoint inhibitor (PD-1/PD-L1 blockade) results in synergistic anti-lymphoma immunity effects.

These findings uncover a novel mechanistic link between CREBBP mutation and immune surveillance dysfunction in lymphomas that can be counteracted by an HDAC3 inhibitor, providing a potentially game-changing approach for restoring anti-tumor immunity.

“HDAC3 inhibition provides an attractive therapeutic avenue for DLBCL and FL and may have enhanced potency in CREBBP-mutant tumors,” says Dr. Melnick. “We are very excited to translate this research into clinical trials that could potentially lead to the development of novel mechanism-based immune epigenetic therapy for CREBBP-mutant lymphomas.”

 

Our Team’s Take on the Most Influential ASH 2018 Lymphoma Research

At the end of each year, the American Society of Hematology (ASH) Annual Meeting & Exposition brings together over 25,000 hematology professionals from around the world to discuss the latest research into the treatment of blood diseases. Highlights of ASH is a two-day program designed to update clinicians and researchers unable to attend the Annual Meeting with the findings most likely to impact daily clinical practice.

Our Lymphoma Program Chief, Dr. Peter Martin was selected to represent the Highlights of ASH Lymphoma Committee for a post-meeting update in January 2019. Here’s his take on the latest lymphoma research.

Diffuse Large B-Cell Lymphoma (DLBCL)

According to the FLYER study, patients younger than 60 with low-risk diffuse large B-cell lymphoma (DLBCL) had excellent outcomes with a shortened regimen of four cycles of R-CHOP chemotherapy versus the standard six cycles. The reduction in chemotherapy may allow for minimizing potential toxic side effects for this patient population.

Our Team’s Take
It is now clear that most young people with stage 1, low-risk DLBCL can be effectively treated with just four cycles of R-CHOP, but providers should use caution in extrapolating these results to rarer subtypes of DLBCL (e.g., primary mediastinal B-cell lymphoma, transformed lymphomas, etc.) that may not have been included in large numbers in the FLYER trial.

SOURCE 781- Excellent Outcome of Young Patients (18-60 years) with Favourable-Prognosis Diffuse Large B-Cell Lymphoma (DLBCL) Treated with 4 Cycles CHOP Plus 6 Applications of Rituximab: Results of the 592 Patients of the Flyer Trial of the Dshnhl/GLA

R-CHOP chemotherapy is the standard treatment for people with previously untreated DLBCL. The Bruton’s tyrosine kinase (BTK) inhibitor ibrutinib has shown activity in people with a subtype of DLBCL known as non-germinal center B cell DLBCL (non-GCB DLBCL) whose disease has relapsed following treatment. The phase III PHOENIX trial examined whether adding ibrutinib to R-CHOP would improve treatment efficacy in previously untreated non-GCB DLBCL patients. Results demonstrated that R-CHOP plus ibrutinib was equivalent to R-CHOP alone. The study did note, however, that ibrutinib may provide some benefit in patients older than 60.

Our Team’s Take
For now, R-CHOP remains the gold-standard for most people with DLBCL, including non-GCB DLBCL. That said, it appears that BTK inhibitors have the potential to improve outcomes if the optimal patient population can be identified.

SOURCE 784 – A Global, Randomized, Placebo-Controlled, Phase 3 Study of Ibrutinib Plus Rituximab, Cyclophosphamide, Doxorubicin, Vincristine, and Prednisone (RCHOP) in Patients with Previously Untreated Non-Germinal Center B-Cell-like (GCB) Diffuse Large B-Cell Lymphoma (DLBCL)

Follicular Lymphoma

Our own Dr. John Leonard led the global phase III AUGMENT clinical trial comparing the efficacy and safety of combined lenalidomide plus rituximab versus rituximab alone in people with previously treated indolent lymphoma, including follicular and marginal zone lymphoma. Lenalidomide-rituximab treatment resulted in superior progression-free survival (PFS) and overall survival (OS) outcomes when compared to rituximab treatment alone, representing an important new treatment option for this patient population.

Our Team’s Take
The impressive overall survival benefit seen in the AUGMENT trial implies that single-agent rituximab may no longer be appropriate for some people with previously treated follicular lymphoma.

SOURCE 445 – AUGMENT: A Phase III Randomized Study of Lenalidomide Plus Rituximab (R2) Vs Rituximab/Placebo in Patients with Relapsed/Refractory Indolent Non-Hodgkin Lymphoma

Hodgkin Lymphoma

A currently accepted standard of care treatment for early-stage low-risk Hodgkin lymphoma is two cycles of ABVD chemotherapy followed by radiotherapy. In the HD16 trial examining the possibility of omitting radiotherapy from the treatment regimen, investigators found that two cycles of ABVD alone does not provide adequate disease control.

Our Team’s Take
A primary goal of cancer care is to deliver a maximally effective treatment regimen while sparing patients from excessive treatment-related side effects. Yet, this research demonstrates that two cycles of ABVD alone does not provide sufficient control of early-stage, favorable risk classical Hodgkin lymphoma. Outside of clinical trials, providers should consider either the addition of radiation or additional chemotherapy.

SOURCE 925 – PET-Guided Treatment of Early-Stage Favorable Hodgkin Lymphoma: Final Results of the International, Randomized Phase 3 Trial HD16 By the German Hodgkin Study Group)

T-Cell Lymphoma

Following the positive results of a phase I trial combining brentuximab vedotin (BV) with CHP (CHOP chemotherapy minus vincristine) in frontline treatment of T-cell lymphoma, researchers tested the combination in patients with newly diagnosed CD30+ anaplastic large cell lymphoma (ALCL), a type of T-cell lymphoma, in the ECHELON-2 trial. Brentuximab vedotin plus CHP was shown to produce better outcomes than standard CHOP for these patients.

Our Team’s Take
BV-CHP represents a new standard of care for anaplastic large cell lymphoma (ALK-positive and ALK-negative). It is less clear that BV adds significantly to CHOP in non-ALCL T-cell lymphomas regardless of CD30 status.

SOURCE 997 – The ECHELON-2 Trial: Results of a Randomized, Double-Blind, Active-Controlled Phase 3 Study of Brentuximab Vedotin and CHP (A+CHP) Versus CHOP in the Frontline Treatment of Patients with CD30+ Peripheral T-Cell Lymphomas

BONUS: Chimeric Antigen Receptor (CAR) T Cell Update

Multiple observational studies suggested that commercial, FDA-approved CAR T cell products used as part of standard practice resulted in outcomes that were comparable to outcomes seen in clinical trials prior to the approval of CAR T cells. Even patients with characteristics that might have resulted in exclusion from clinical trials (e.g., low blood counts) appeared to have comparable outcomes.

Our Team’s Take
CAR T cells clearly have a role in people with treatment-refractory DLBCL. Nonetheless, more research will be required to further improve the efficacy and safety of CAR T cells so that patients outside of academic medical centers might have access to this new treatment approach.

SOURCE 91 – Axicabtagene Ciloleucel (Axi-cel) CD19 Chimeric Antigen Receptor (CAR) T-Cell Therapy for Relapsed/Refractory Large B-Cell Lymphoma: Real World Experience; 92 – Axicabtagene Ciloleucel in the Real World: Outcomes and Predictors of Response, Resistance and Toxicity

 

2018 American Society of Hematology (ASH) Annual Meeting

The American Society of Hematology (ASH) is the world’s largest professional society serving clinicians and scientists who work to conquer blood diseases. The ASH Annual Meeting & Exposition brings together over 25,000 hematology professionals from around the world to discuss the understanding, diagnosis, treatment, and prevention of disorders affecting the blood, bone marrow, and immunologic, hemostatic and vascular systems.

This year, the ASH Meeting celebrated its 60th anniversary in San Diego, CA. As always, our team was proud to contribute new lymphoma discoveries for presentation at the meeting. Here are some research highlights from our team.


Dr. John Leonard led a global phase III clinical trial comparing the efficacy and safety of combined lenalidomide plus rituximab versus rituximab alone in people with previously treated indolent lymphoma, including follicular and marginal zone lymphoma. Results demonstrating lenalidomide-rituximab as an important new treatment option for this patient population.

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Dr. Richard Furman and colleagues found that at follow-up of up to seven years, ibrutinib demonstrated sustained activity in both first line and relapsed/refractory chronic lymphocytic leukemia (CLL) patients.

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Dr. Peter Martin led a study examining the safety and efficacy of CC-486, also known as oral azacitidine, plus R-CHOP chemotherapy in people with diffuse large B-cell lymphoma (DLBCL).

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Using a combination of human, animal, and cell line data, Jude Phillip, PhD, of the Leandro Cerchietti Research Lab, and colleagues found that the internal architecture of lymphomas present important insights into disease progression.

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Dr. John Allan presented a preliminary update of an ongoing first-in-human study of vecabrutinib in patients with advanced B-cell malignancies.

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Dr. Sarah Rutherford reported data that may support the elimination of bone marrow biopsies in follicular lymphoma and diffuse large B-cell lymphoma clinical trials.

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Dr. Richard Furman and colleagues found that venetoclax is well tolerated and produces high levels of response in previously treated Waldenstrom’s macroglobulinemia patients.

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We are proud of our team’s continued commitment to advancing the overall understanding of lymphoma and improving clinical outcomes and quality of life for all those affected by the disease.