NEW ORLEANS—The TLR9 agonist SD-101 has produced encouraging early results in patients with low-grade B-cell lymphoma, according to researchers.
In an ongoing phase 1/2 study, patients received low-dose radiation, followed by an injection of SD-101 into one of their tumors.
This prompted changes in the tumor microenvironment that potentially induced a systemic antitumor response and decreased the volume of both treated and untreated tumors.
In addition, SD-101 was considered well tolerated, with no dose-limiting toxicities or maximum-tolerated dose.
“We are pleased to have already demonstrated a safety profile, pharmacodynamics, and preliminary efficacy in this study,” said Ronald Levy, MD, of Stanford University in California.
Dr Levy and his colleagues presented these results at the 2016 AACR Annual Meeting (abstract CT047). The study is sponsored by Dynavax Technologies Corporation, the company developing SD-101.
The researchers reported data for 13 patients with untreated, low-grade B-cell lymphoma. They had a mean age of 63.2, and 53.8% were male.
Patients had follicular lymphoma (n=9), small lymphocytic lymphoma (n=2), chronic lymphocytic leukemia (n=1), and nodal marginal zone lymphoma (n=1).
At least 2 sites of measurable disease were required for participation in this study. One site was treated with low-dose radiation (2 Gy) and injected with SD-101 on days 1, 8, 15, 22, and 29. Other lesions received no treatment.
In Part 1—the dose-escalation portion of the study—patients received SD-101 at 1 mg (n=3), 2 mg (n=3), 4 mg (n=3), or 8 mg (n=4). The phase 2 expansion portion of the study is ongoing, with enrollment in 2 dose cohorts (1 mg and 8 mg).
“This clinical trial design is unique and takes advantage of the fact that lymphoma patients have easily injectable sites of disease,” Dr Levy said. “The local injections are conveniently added to low-dose radiotherapy, a standard treatment for low-grade lymphoma.”
All 13 patients experienced at least 1 adverse event (AEs), although nearly all were grade 1 or 2.
The most common treatment-related AEs were local injection-site reactions and flu-like symptoms, including fever, chills, and myalgia (n=11 for all 3). However, the researchers said these AEs were primarily short-lived and controlled by over-the-counter acetaminophen in most cases.
In the 8 mg dosing cohort, 1 patient had grade 3 neutropenia and 2 had grade 3 malaise, all of which were considered treatment-related. In addition, there was a case of grade 3 asymptomatic pulmonary embolism in the 4 mg dose cohort, which was deemed serious but unrelated to treatment.
The researchers observed induction of interferon-responsive genes at all dose levels 24 hours after the second dose of SD-101 was given (Day 9).
In addition, T-cell numbers increased at the treated site by Day 8. The total T cells increased in 7 of 10 evaluable patients by Day 8 (range, >300% to 18%).
CD4+ and CD8+ T cells increased simultaneously in 5 of 7 evaluable patients, regulatory T cells decreased in 8 of 10 evaluable patients by Day 8, and follicular T helper cells decreased in 9 of 9 evaluable patients by Day 8.
Furthermore, treated and untreated tumors decreased in volume across all dose groups.
At Day 90, 12 patients had a reduction of the product of diameters in treated tumors (median -45.3%; range, -87 to +100), and 11 patients had a reduction in untreated tumors (median -8.1%; range, -48 to +45).
In 9 patients, these abscopal effects were sustained for at least 180 to 360 days.
However, 6 patients discontinued from the study due to progression. Three had radiographic progression—1 at Day 92 (in the 4 mg cohort) and 2 at 1 year (1 in the 1 mg cohort and 1 in the 2 mg cohort).
Two patients had clinical progression—1 at Day 197 (4 mg) and 1 at Day 273 (2 mg). And 1 patient discontinued at Day 203 due to a combination of clinical and radiographic progression (8 mg).
The researchers pointed out that there was no evidence of a dose response with SD-101, but the study included a limited number of patients.