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Growing monoclonal antibodies
Photo by Linda Bartlett

LUGANO—The defucosylated monoclonal antibody (mAb) ARGX-110, which is active against CD70-bearing tumor cells and CD70-dependent stimulation of regulatory T cells, has shown activity in relapsed/refractory T-cell lymphoma (TCL), according to investigators.

Of the 8 TCL patients enrolled in a phase 1 trial of ARGX-110, 3 had a biological response to the mAb.

In this dose-escalation trial, the maximum tolerated dose of ARGX-110 was not reached.

Marie Maerevoet, MD, of the Institut Jules Bordet in Brussels, Belgium, presented results from the lymphoma cohort of this trial at the 13th International Congress on Malignant Lymphoma (abstract 040*). The study was sponsored by arGEN-X, the company developing ARGX-110.

Dr  Maerevoet pointed out that more than half the tumor cells in 71% of patients with cutaneous T-cell lymphoma (CTCL) and 22% with peripheral T-cell lymphoma (PTCL) are CD70-positive. CD70 signaling occurs via CD27, and CD27 shedding is a biomarker for an active pathway.

Since ARGX-110 has an affinity for CD70, inhibits CD27 signaling, and mediates the lysis of TCL in Sézary syndrome (SS), mycosis fungoides, and anaplastic large cell lymphoma (ALCL) cell lines, researchers decided to investigate the safety and clinical pharmacology of ARGX-110 monotherapy in metastatic, relapsed or refractory, solid tumors and hematologic malignancies.

Patients’ tumors had to express CD70 by immunohistochemistry, defined as more than 10% tumor cells of 2+ or 3+ intensity.

The primary endpoint was to determine the maximum tolerated dose. Secondary endpoints were pharmacology, immunogenicity, and efficacy signals.

Patient demographics

Between February 2013 and April 2015, investigators assigned 63 patients to receive ARGX-110 at doses ranging from 0.1 to 10 mg/kg intravenously once every 3 weeks until disease progression or withdrawal due to toxicity. Patients were pre-medicated with corticoid regimens.

Eighteen patients had lymphoid malignancies—8 with B-cell lymphomas, 8 with TCL, and 2 with Hodgkin lymphoma.

The TCL cohort consisted of 1 patient with SS, 1 with transformed SS, 1 with T-helper CTCL, 2 with angioimmunoblastic T-cell lymphoma (AITL), 2 with PTCL not otherwise specified (NOS), and 1 with ALCL.

Patients were a median age of 62 (range, 55–78), had a median of 4 prior treatment regimens (range, 2–6), and received a median of 2 cycles of ARGX-110 (range, 1–6).

Dr Maerevoet noted that most lymphoma patients received a dose of 5 mg/kg every 3 weeks.

Safety

In the entire lymphoma cohort of 18 patients, 4 patients (22%) experienced a grade 1 or 2 infusion-related reaction. Three patients (18%) developed grade 3 sepsis—1 with Waldenstrom’s macroglobulinemia, 1 with AITL, and 1 with PTCL-NOS.

Two patients (11%) had hematologic toxicity consisting of a grade 3 decrease in hemoglobin and absolute neutrophil count, which was considered not related to treatment with ARGX-110.

“The maximum tolerated dose was not reached,” Dr Maerevoet said. “We didn’t observe auto-immune adverse events or impact on serum IgG or IgM.”

Efficacy outcomes

The main reason for withdrawal was progressive disease, which occurred in 14 lymphoma patients.

Two patients—1 with Waldenstrom’s macroglobulinemia and 1 with AITL—withdrew due to adverse events of sepsis (catheter infection, pneumonia), 1 patient with SS withdrew for social reasons, and 1 patient with follicular T-cell lymphoma (currently classified as PTCL-NOS) remains on study.

Dr Maerevoet described the 3 TCL patients who had a biologic response to ARGX-110. One patient with SS had a hematologic complete remission after 6 cycles at the 0.1 mg/kg dose.

Another patient with transformed SS experienced a depletion of circulating clones after 2 cycles of the 10 mg/kg dose. However, the patient ultimately died of progressive disease.

A third patient had resolution of autoimmune hemolytic anemia. This 61-year-old male with AITL achieved a partial response with normalization of LDH levels and an increase in hemoglobin to 7.9 g/dL without transfusion support after 2 doses of ARGX-110 at 5 mg/kg.

The patient became Coombs-negative and had a 16% reduction in tumor size by CT scan. However, the patient subsequently died of pneumonia.

The investigators also observed clinical activity in the peripheral blood, lymph nodes, and skin of 2 additional patients.

The biological activity of ARGX-110 as demonstrated by these TCL patients, in addition to the safety and tolerability of this mAb, led the team to conclude that further clinical investigation of ARGX-110 in TCL is warranted. end hematology article

*Information in the abstract differs from that presented at the meeting.


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