First-in-Human Phase I Study of ABBV-838, an Antibody-Drug Conjugate Targeting SLAMF7/CS1 in Patients with Relapsed and Refractory Multiple Myeloma.

PURPOSE: ABBV-838 is an antibody-drug conjugate targeting a unique epitope of CD2 subset 1, a cell-surface glycoprotein expressed on multiple myeloma cells. This phase I/Ib first-in-human, dose-escalation study (trial registration ID: NCT02462525) evaluated the safety, pharmacokinetics, and preliminary activity of ABBV-838 in patients with relapsed and refractory multiple myeloma (RRMM). PATIENTS AND METHODS: Eligible patients (≥18 years) received ABBV-838 (3+3 design) intravenously starting from 0.6 mg/kg up to 6.0 mg/kg for 3-week dosing intervals (Q3W). Patients could continue ABBV-838 for up to 24 months. Assessment of alternate dosing intervals (Q1W and Q2W) was conducted in parallel. RESULTS: As of March 2017, 75 patients received at least one dose of ABBV-838. The most common any-grade treatment-emergent adverse events (TEAE) were neutropenia and anemia (28.0% each), fatigue (26.7%), and nausea (25.3%). Grade 3/4/5 TEAEs were reported in 73.3% of patients across all treatment groups; most common were neutropenia (20.0%), anemia (18.7%), and leukopenia (13.3%). Grade 3/4/5 ABBV-838-related TEAEs were reported by 40.0% of patients across all treatment groups. Overall, 4.0% of patients experienced TEAEs leading to death, none ABBV-838 related. The MTD was not reached; the selected recommended dose for the expansion cohort was 5.0 mg/kg Q3W. Pharmacokinetic analysis showed that exposure was approximately dose proportional. The overall response rate was 10.7%; very good partial responses and partial responses were achieved by 2 (2.7%) and 6 (8.0%) patients, respectively. CONCLUSIONS: These results demonstrate that ABBV-838 is safe and well-tolerated in patients with RRMM with a very limited efficacy.

The CD25-binding antibody Daclizumab High-Yield Process has a distinct glycosylation pattern and reduced antibody-dependent cell-mediated cytotoxicity in comparison to Zenapax®.

The CD25-binding antibody daclizumab high-yield process (DAC HYP) is an interleukin (IL)-2 signal modulating antibody that shares primary amino acid sequence and CD25 binding affinity with Zenapax®, a distinct form of daclizumab, which was approved for the prevention of acute organ rejection in patients receiving renal transplants as part of an immunosuppressive regimen that includes cyclosporine and corticosteroids. Comparison of the physicochemical properties of the two antibody forms revealed the glycosylation profile of DAC HYP differs from Zenapax in both glycan distribution and the types of oligosaccharides, most notably high-mannose, galactosylated and galactose-α-1,3-galactose (α-Gal) oligosaccharides, resulting in a DAC HYP antibody material that is structurally distinct from Zenapax. Although neither antibody elicited complement-dependent cytotoxicity in vitro, DAC HYP antibody had significantly reduced levels of antibody-dependent cell-mediated cytotoxicity (ADCC). The ADCC activity required natural killer (NK) cells, but not monocytes, suggesting the effects were mediated through binding to Fc-gamma RIII (CD16). Incubation of each antibody with peripheral blood mononuclear cells also caused the down-modulation of CD16 expression on NK cells and the CD16 down-modulation was greater for Zenapax in comparison to that observed for DAC HYP. The substantive glycosylation differences between the two antibody forms and corresponding greater Fc-mediated effector activities by Zenapax, including cell killing activity, manifest as a difference in the biological function and pharmacology between DAC HYP and Zenapax.

Blockade of the High-Affinity Interleukin-2 Receptors with Daclizumab High-Yield Process: Pharmacokinetic/Pharmacodynamic Analysis of Single- and Multiple-Dose Phase I Trials.

BACKGROUND AND OBJECTIVE: Daclizumab high-yield process (DAC HYP) is a humanized monoclonal antibody that selectively blocks the α-subunit (CD25) of the high-affinity interleukin-2 receptors, and has shown robust efficacy as a treatment for multiple sclerosis (MS). This work quantitatively characterized the relationship between DAC HYP serum concentrations and saturation of CD25 expressed on antigen-rich target T cells in blood. METHODS: Serial pharmacokinetic and 968 CD25 measurements from three double-blind, randomized, placebo-controlled, phase I studies of DAC HYP (50-300 mg subcutaneous and 200-400 mg intravenous doses or placebo) in healthy volunteers (n = 95) were analyzed using nonlinear mixed-effects modeling. CD25 occupancy was determined using flow cytometry and a fluorescently-labeled DAC HYP-competing antibody. RESULTS: CD25 occupancy was described using a direct inhibitory sigmoidal maximum effect (E max) model (where DAC HYP fully inhibited CD25 labeling with competing antibody). Two IC50 (serum concentration corresponding to 50 % of maximal inhibition) parameters were used to describe rapid CD25 saturation at initiation of dosing and apparently slower desaturation during DAC HYP washout. Parameter estimates (95 % bootstrap confidence intervals) were: baseline CD25 labeling, 47 % (45-48); DAC HYP IC50(saturation), 0.023 µg/mL (0.005-0.073); IC50(desaturation) 0.86 µg/mL (0.74-0.98); Hill coefficient 5.6 (4.3-6.8). CONCLUSIONS: Based on the developed model, the 150 mg monthly subcutaneous regimen of DAC HYP in subjects with MS is predicted to saturate CD25 on target effector T cells within a few hours of dosing and maintain CD25 saturation during the entire dosing interval. Free CD25 levels return to baseline within 4-6 months of the last DAC HYP dose.

In vivo maintenance of human regulatory T cells during CD25 blockade.

Regulatory T cells (Tregs) mediate immune tolerance to self and depend on IL-2 for homeostasis. Treg deficiency, dysfunction, and instability are implicated in the pathogenesis of numerous autoimmune diseases. There is considerable interest in therapeutic modulation of the IL-2 pathway to treat autoimmunity, facilitate transplantation tolerance, or potentiate tumor immunotherapy. Daclizumab is a humanized mAb that binds the IL-2 receptor a subunit (IL-2R a or CD25) and prevents IL-2 binding. In this study, we investigated the effect of daclizumab-mediated CD25 blockade on Treg homeostasis in patients with relapsing-remitting multiple sclerosis. We report that daclizumab therapy caused an ~50% decrease in Tregs over a 52-wk period. Remaining FOXP3+ cells retained a demethylated Treg-specific demethylated region in the FOXP3 promoter, maintained active cell cycling, and had minimal production of IL-2, IFN- g, and IL-17. In the presence of daclizumab, IL-2 serum concentrations increased and IL-2R bg signaling induced STAT5 phosphorylation and sustained FOXP3 expression. Treg declines were not associated with daclizumab-related clinical benefit or cutaneous adverse events. These results demonstrate that Treg phenotype and lineage stability can be maintained in the face of CD25 blockade.

Daclizumab, an IL-2 modulating antibody for treatment of multiple sclerosis.

Daclizumab is a monoclonal antibody specific for the IL-2R α chain (CD25). Daclizumab has been observed to have multiple mechanisms of action, which may contribute to beneficial effects in immune-related disease and particularly in relapsing and remitting multiple sclerosis (RRMS). These include inhibition of activated immune cells, increase of regulatory natural killer cells, effects on dendritic cells, inhibition of innate lymphoid tissue inducer cells and altered responses involving IL-2 transpresentation. The antibody has shown considerable promise in open-label and early Phase II clinical trials when used as a monotherapy, or in combination with IFN-ß. In recently completed randomized trials in RRMS, treatment with daclizumab monotherapy compared with placebo resulted in clinically meaningful and statistically significant reductions in relapses, active lesions on brain MRI and slowing of disability progression. A large Phase III trial in RRMS is ongoing.

Intermediate-affinity interleukin-2 receptor expression predicts CD56(bright) natural killer cell expansion after daclizumab treatment in the CHOICE study of patients with multiple sclerosis.

OBJECTIVE: The objective of this study was to evaluate whether interleukin-2 (IL-2) receptor expression on CD56(bright) natural killer (NK) cells predicted CD56(bright) NK cell expansion and therapeutic response to daclizumab (DAC) in multiple sclerosis (MS). METHODS: DAC exposure, CD56(bright) NK cell counts, IL-2 receptor alpha (CD25) and beta (CD122) subunits, and new or enlarged lesions on brain MRI were measured in 64 subjects in a pharmacokinetic/pharmacodynamic substudy of the phase 2 CHOICE trial at multiple time points. Peripheral blood mononuclear cell (PBMC) samples were obtained from healthy subjects to assess the relationship among DAC treatment, intermediate affinity IL-2 signaling, and CD56(bright) NK cell expansion. RESULTS: Increased CD56(bright) NK cell counts in DAC/interferon beta (IFNß)-treated subjects were observed by day 14, the first post-dosing time point (mean [SD] ln{CD56(bright) NK cell count}: DAC high/IFNß, 2.01 [1.25]; DAC low/IFNß, 2.29 [1.06]; placebo/IFNß, 1.01 [1.03]; adjusted p = 0.003), and persisted throughout the treatment period. Higher DAC dose predicted a faster rate of CD56(bright) NK cell expansion (p < 0.001), but individual subjects' increases in CD56(bright) NK cells from baseline levels were only weakly correlated with DAC exposure (r(2) = 0.167). Higher expression of the intermediate-affinity IL-2 receptor subunit (CD122) on CD56(bright) NK cells at baseline predicted fewer new gadolinium-enhanced (Gd+) lesions during the treatment period (1.77 vs. 0.62 adjusted mean new Gd+ lesions during weeks 8-24, lowest vs. highest quartile of percentage CD122(+) CD56(bright) NK cells; p = 0.033) and a greater increase in CD56(bright) NK cell counts at the end of DAC dosing (p = 0.029). CONCLUSION: CD56(bright) NK cell expansion after DAC treatment appears to reflect individual differences in the capacity for intermediate-affinity IL-2 signaling and could provide a basis for predicting clinical response to DAC in MS.