# Dissecting the mechanism of cyclophosphamide-enhanced antibody efficacy

> **NIH NIH R21** · MASSACHUSETTS INSTITUTE OF TECHNOLOGY · 2020 · $222,888

## Abstract

Antibody therapy is a core component of treatment regimens for B cell lymphoma, yet a subset of these
malignancies are refractory to front-line therapy. Nearly 10% of aggressive B-cell lymphomas harbor
chromosome rearrangements involving the MYC and BCL2 (or BCL6) oncogenes. These so called “double-hit
lymphoma (DHLs)” are associated with very poor prognosis with standard chemo-immunotherapy. In addition,
25-30% of DLBCLs without MYC rearrangements have protein over-expression of MYC and BCL2. These
lymphomas (so-called “double overexpressing lymphomas (DOL)”) also have very high rates of primary
treatment failure. Combined, these tumors represent a significant fraction of currently incurable DLBCL. The
Hemann laboratory recently developed a treatment refractory humanized mouse model of DHL amenable to
treatment with therapeutic antibodies. Specifically, B-cell-specific co-expression of the oncogenes MYC and
BCL2 in human hematopoietic stem cells and adoptive transferred to NSG mice resulted in the rapid
development of an aggressive human malignancy that effectively recapitulated the pathological and clinical
characteristics of DHL. Like human DHL, the model lymphomas had low/no expression of CD20, suggesting
that rituximab (a core component of current lymphoma treatment regimes) would have minimal effects.
However, the cells highly expressed surface CD52, the target of alemtuzumab. The combination of
alemtuzumab and cyclophosphamide (CTX) yielded a strikingly synergistic (~160-fold) therapeutic effect,
leading to near-complete elimination of disease in all sites. The synergy of alemtuzumab and CTX was very
specific to this drug combination, as co-dosing alemtuzumab with other chemotherapies failed to produce a
synergistic effect. CTX induced the expression of the pro-phagocytic factor calreticulin and reduced expression
of the “don't eat me” signal CD47 on tumor cells. To confirm that the same effects occur in human DHL, we
xenografted specimens obtained from patients with relapsed/refractory DHL. In both models (which also
express high levels of CD52), treatment with the combination was markedly synergistic, with near or complete
eradication of disease after a single cycle of treatment with the combination, but not with either single agent.
While this work represents a significant first step in the development of effective treatment for DHL, very little
is known about the mechanism of this drug-antibody synergy. The focus of this proposal is to understand the
molecular basis by which CTX promotes the efficacy of therapeutic antibodies and to identify basic principles
of antibody/drug combination therapy that will expand and enhance their clinical use. Together, these studies
will define the mechanisms and broader applicability of CTX/antibody combinations that could be immediately
applied in patients with relapsed/refractory lymphomas or other conditions dependent upon antibody-mediated
cytotoxicity.

## Key facts

- **NIH application ID:** 9957908
- **Project number:** 1R21AI151827-01
- **Recipient organization:** MASSACHUSETTS INSTITUTE OF TECHNOLOGY
- **Principal Investigator:** Michael Hemann
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $222,888
- **Award type:** 1
- **Project period:** 2020-03-04 → 2022-02-28

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9957908

## Citation

> US National Institutes of Health, RePORTER application 9957908, Dissecting the mechanism of cyclophosphamide-enhanced antibody efficacy (1R21AI151827-01). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/9957908. Licensed CC0.

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