Targeting Multiple Myeloma with AMG 424, a Novel Anti-CD38/CD3 Bispecific T-cell-recruiting Antibody Optimized for Cytotoxicity and Cytokine Release.

PURPOSE: Despite advances in the treatment of multiple myeloma, new therapies are needed to induce more profound clinical responses. T-cell-redirected lysis triggered by bispecific antibodies recruiting T cells to cancer cells is a clinically validated mechanism of action against hematologic malignancies and CD38 is a tumor-associated antigen with near-universal expression in multiple myeloma. Thus, an anti-CD38/CD3 bispecific T-cell-recruiting antibody has the potential to be an effective new therapeutic for multiple myeloma. EXPERIMENTAL DESIGN: Anti-CD38/CD3 XmAb T-cell-recruiting antibodies with different affinities for CD38 and CD3 were assessed in vitro and in vivo for their redirected T-cell lysis activity against cancer cell lines, their lower levels of cytokine release, and their potency in the presence of high levels of soluble CD38. Select candidates were further tested in cynomolgus monkeys for B-cell depletion and cytokine release properties. RESULTS: AMG 424 was selected on the basis of its ability to kill cancer cells expressing high and low levels of CD38 in vitro and trigger T-cell proliferation, but with attenuated cytokine release. In vivo, AMG 424 induces tumor growth inhibition in bone marrow-invasive mouse cancer models and the depletion of peripheral B cells in cynomolgus monkeys, without triggering excessive cytokine release. The activity of AMG 424 against normal immune cells expressing CD38 is also presented. CONCLUSIONS: These findings support the clinical development of AMG 424, an affinity-optimized T-cell-recruiting antibody with the potential to elicit significant clinical activity in patients with multiple myeloma.

Structure-Function Relationships for Recombinant Erythropoietins: A Case Study From a Proposed Manufacturing Change With Implications for Erythropoietin Biosimilar Study Designs.

Comparability studies used to assess a proposed manufacturing change for a biological product include sensitive analytical studies to confirm there are no significant differences in structural or functional attributes that may contribute to clinically meaningful changes in efficacy or safety. When a proposed change is relatively complex or when clinically relevant differences between the product before and after the change cannot be ruled out based on analytical studies, nonclinical and clinical bridging studies are generally required to confirm overall comparability. In this study, we report findings from a comparability assessment of epoetin alfa before and after a proposed manufacturing process change. Although differences in glycosylation attributes were observed, these were initially believed to be irrelevant to the product's pharmacology. This assumption was initially supported via nonclinical and clinical pharmacology studies, but a clinically meaningful difference in potency was ultimately observed in a phase 3 clinical study conducted in a sensitive patient population using a sensitive study design. These results indicate that the nonclinical assessments of structure-function relationships were insufficiently sensitive to identify clinically relevant differences resulting from differences in the glycosylation profile. This case study highlights important findings that may be relevant in the development of biosimilar epoetin alfa products.

Bispecific T cell engager (BiTE®) antibody constructs can mediate bystander tumor cell killing.

For targets that are homogenously expressed, such as CD19 on cells of the B lymphocyte lineage, immunotherapies can be highly effective. Targeting CD19 with blinatumomab, a CD19/CD3 bispecific antibody construct (BiTE®), or with chimeric antigen receptor T cells (CAR-T) has shown great promise for treating certain CD19-positive hematological malignancies. In contrast, solid tumors with heterogeneous expression of the tumor-associated antigen (TAA) may present a challenge for targeted therapies. To prevent escape of TAA-negative cancer cells, immunotherapies with a local bystander effect would be beneficial. As a model to investigate BiTE®-mediated bystander killing in the solid tumor setting, we used epidermal growth factor receptor (EGFR) as a target. We measured lysis of EGFR-negative populations in vitro and in vivo when co-cultured with EGFR-positive cells, human T cells and an EGFR/CD3 BiTE® antibody construct. Bystander EGFR-negative cells were efficiently lysed by BiTE®-activated T cells only when proximal to EGFR-positive cells. Our mechanistic analysis suggests that cytokines released by BiTE®-activated T-cells induced upregulation of ICAM-1 and FAS on EGFR-negative bystander cells, contributing to T cell-induced bystander cell lysis.

Romiplostim promotes platelet recovery in a mouse model of multicycle chemotherapy-induced thrombocytopenia.

Chemotherapy-induced thrombocytopenia can lead to chemotherapy treatment delays or dose reductions. The ability of romiplostim, a thrombopoietin (TPO) mimetic, to promote platelet recovery in a mouse model of multicycle chemotherapy/radiation therapy (CRT)-induced thrombocytopenia was examined. In humans, an inverse relationship between platelet counts and endogenous TPO (eTPO) concentration exists. In a CRT mouse model, eTPO was not elevated during the first 5 days after CRT treatment (the "eTPO gap"), then increased to a peak 10 days after each CRT treatment in an inverse relationship to platelet counts seen in humans. To bridge the eTPO gap, mice were treated with 10-1,000 µg/kg of romiplostim on day 0, 1, or 2 after CRT. In some mice, the romiplostim dose was approximately divided over 3 days. Platelet recovery occurred faster with romiplostim in most conditions tested. Romiplostim doses of ≥100 µg/kg given on day 0 significantly lessened the platelet nadir. Fractionating the dose over 3 days did not appear to confer a large advantage. These data may provide a rationale for clinical studies of romiplostim in chemotherapy-induced thrombocytopenia.