Abscopal Effect of Radiotherapy and Nivolumab in Relapsed or Refractory Hodgkin Lymphoma (AERN): An International Multicenter Single-Arm Two-Stage Phase II GHSG Trial

Background

The anti-PD1 antibodies nivolumab and pembrolizumab are approved for relapsed or refractory classical Hodgkin lymphoma (r/r cHL) due to high overall response rates (ORR) with a favorable safety profile. However, complete responses (CR) are rare, and patients eventually develop progressive disease. Treatment options in this situation are very limited and usually regarded palliative. Innovative therapies for patients with progressive r/r cHL or insufficient response to anti-PD1 antibodies are hence an unmet clinical need.

Radiotherapy (RT) is highly effective and potentially curative in cHL. Local RT results in immunogeneic cell-death at times leading to immune-mediated systemic effects termed abscopal response (AR). Case reports in different cancers including cHL highlight this effect of local therapies potentially enhanced by systemic immunotherapies. Combining the approved systemic anti-PD1 treatment with local RT to a single cHL lesion might hence work synergistically and result in improved tumor control with limited additional toxicity. It thereby would constitute a viable therapeutic option for patients with r/r cHL and could in the future also be incorporated in earlier lines of therapy.

However, prospective data regarding this treatment strategy is lacking and will be generated with the recently activated herein presented GHSG AERN trial.

Study Design & Methods

AERN is an investigator-sponsored, prospective, international, multicenter, single-arm, two-stage phase II trial (NCT03480334) conducted at 10 European trial sites in Austria, Germany, United Kingdom, Netherlands and Norway.

Patients with r/r cHL on active anti-PD1 therapy >18 years of age without serious concomitant diseases or organ dysfunction are eligible for enrollment. Patients either have to present with progressive disease (PD) or stable disease (SD) >6 months as best response to the ongoing anti-PD1 antibody. After registration for the screening phase, eligibility will be verified by a centralized GHSG review facility who will also define a single target lesion for RT to ensure at least one cHL lesion outside the 10% RT isodose for evaluation of the primary endpoint (abscopal response rate after 6x nivolumab, ARR-6). All patients will receive 240mg nivolumab at 2-weekly intervals and 20 Gy RT to the target lesion at 2 Gy fractions on ten consecutive working days starting day 6 of nivolumab treatment. Nivolumab will be discontinued in case of inacceptable toxicity or further disease progression and continued for a maximum of 18 months within the AERN trial.

During the first stage of the trial, 9 qualified patients will be treated and their response to treatment will be centrally evaluated after the first 6 nivolumab doses. If no AR is observed in stage I, the trial will be terminated for futility. Otherwise 20 additional patients will be enrolled into the second stage for a total trial population of 29 r/r cHL patients. The null hypothesis H0: ARR-6 < 5% will be tested against a one-sided alternative at a confidence level of α = 5%, and at least 4 AR need to be observed for the rejection of H0. Secondary endpoints include e.g. ORR, overall ARR, CR rate, PFS and OS but also feasibility aspects, (S)AEs and quality of life (QoL) measures.

To understand the underlying mechanisms of efficacy but also resistance or toxicity a comprehensive set of correlative studies will be conducted. Baseline and sequential blood samples as well as tumor biopsies and rectal swabs for microbiome analyses will be taken during AERN in patients with separate informed consent. This allows detailed evaluation of serological, cellular, functional, histological and genetic parameters to elucidate synergies between anti-PD1 and RT. Ultimately the correlative studies should help to further refine anti-PD1 based combination therapies, ideally beyond the setting of r/r cHL.

In summary AERN, to our knowledge, is the first prospective trial formally evaluating the postulated abscopal effect in r/r cHL. The trial addresses an unmet clinical need in r/r cHL patients with insufficient or lost response to anti-PD1 antibodies. AERN additionally will provide proof-of-concept for a synergy of local RT with checkpoint inhibition substantiated by comprehensive correlative studies in blood, tumor tissue and microbiome. Recruitment has started but preliminary data regarding safety or efficacy are not yet available.

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