Clinical and Biological Evaluation of the Novel CD30/CD16A Tetravalent Bispecific Antibody (AFM13) in Relapsed or Refractory CD30-Positive Lymphoma with Cutaneous Presentation: A Biomarker Phase Ib/IIa Study (NCT03192202)

Introduction: Natural Killer cells (NK cells) play an important role in tumor immune-surveillance. NK-mediated cell killing can occur through distinct mechanisms: (1) by activating the receptor NKG2D and natural cytotoxicity receptors (NCR), and (2) through the potent activating receptor CD16 (FcγRIII) which mediates antibody-dependent cell-mediated cytotoxicity (ADCC). Therapeutic strategies to harness the ability of NK cells to induce an ADCC response are emerging. AFM13 is a CD30/CD16A targeting high affinity bispecific tetravalent antibody that engages and activates NK cells. This study evaluates the ability of AFM13 to engage innate immunity through specific activation and recruitment of NK cells to tumors expressing CD30 and the impact of these effects on clinical outcome. In addition, it examines the immunologic changes in the tumor and peripheral blood as a function of the dose and method of administration of AFM13 over time.

Methods: Subjects with relapsed or refractory CD30 expressing lymphoma with cutaneous involvement were recruited into 3 treatment cohorts: (1) 1.5 mg/kg IV weekly, (2) 7 mg/kg IV weekly and (3) 7 mg/kg continuous intravenous infusion (CIVI) over 5 days weekly. Each cohort consisted of 3 patients. Subjects received 8 weeks of therapy each cycle. Response assessment was performed on week 11 of each cycle by mSWAT, photography, PET imaging and peripheral blood flowcytometry. A second cycle was administered if there was no progression of disease. Subjects underwent mandatory tumor biopsies and peripheral blood immunologic studies during the first cycle of therapy as follows: pretreatment, day 5 post first dose, week 4 and week 8 of therapy. An optional biopsy was also collected at end of study. Tumor biopsies were analyzed and evaluated by a pathologist and IHC image analyzer to characterize immune cell subpopulations. Peripheral blood samples were analyzed by flowcytometry.

Results: Nine subjects were accrued. Their age ranged from 37-79 years, 3 of 9 where white and 6 of 9 were men. The median number of prior therapies was 4 (1-11), 2 patients had progressed on Brentuximab vedotin, and 5 patients received total skin electron beam radiotherapy. The disease etiologies were as follows: 4 patients with transformed mycosis fungoides, 2 patients with systemic anaplastic large cell lymphoma-ALK negative, 2 patients with non- transformed mycosis fungoides and 1 patient with cutaneous anaplastic large cell lymphoma.

Among the 8 subjects who were evaluable for response 4 of 8 (50%) achieved an objective response rate (ORR). In cohort 1 we observed 1 complete response (CR), 1 partial response (PR) and 1 stable disease (SD). In cohort 2, we observed 3 SD. In cohort 3, we observed 2 PRs and one subject awaiting disease assessment. Infusion related reaction (IRR) were observed in 4 of 9 subjects and managed conservatively. Cellulitis was noted in 3 subjects of which 2 developed bacteremia requiring intravenous antibiotics, and was not considered related to AFM13 treatment. There were no other treatment-emergent adverse events.

In the peripheral blood, we observed a decrease in circulating NK cells during therapy (Weeks 1- 8) with post therapy recovery (by week 11) by following cells that were CD56+ CD3- , CD56+ CD16+ and NKp46+ by Flow Cytometry. We observed an increase over time in the expression of the activation marker CD69 on NK cells from responders compared to non-responders. Similarly, tumor biopsies in responders showed increased infiltration of CD56+ NK cells as opposed to non-responders. Flow quantitation of circulating CD4+ CD25+ T cells (Tregs) shows a decrease in responders vs. non-responders.

Conclusions: AFM13 demonstrated a high ORR of 50 % among a population of heavily pretreated patients with a CD30 positive lymphoproliferative T-cell malignancy. AFM 13 exhibited activity post Brentuximab vedotin failure. In addition, biological changes in NK cells may predict response. This data are the first to demonstrate the therapeutic advantages of this bispecific, and the first to correlate changes in NK cells as a function of dose and schedule. AFM13 is able to engage the innate immune system through a specific activation and recruitment of circulating NK cells to tumors expressing CD30. This immunological tumor response may correlate with clinical response. We have begun to expand the patient cohorts, and pursue additional comprehensive correlative studies in this population.