SUMMARY  

• Daratumumab is an IgG1κ human monoclonal antibody (mAb) that binds to CD38 and inhibits the growth of CD38 expressing tumor cells by inducing apoptosis directly through Fc mediated cross linking as well as by immune-mediated tumor cell lysis through complement dependent cytotoxicity (CDC), antibody dependent cell mediated cytotoxicity (ADCC), and antibody dependent cellular phagocytosis (ADCP). A subset of myeloid derived suppressor cells (CD38+MDSCs), regulatory T cells (CD38+T_regs) and B cells (CD38+B_regs) are decreased by daratumumab.^1,2
• van de Donk et al (2017)³ explored the ability of daratumumab to promote adaptive T-cell responses and immune changes and investigated the immunophenotype of natural killer (NK) cells that persist upon treatment with lenalidomide and dexamethasone (Rd) or daratumumab plus Rd (DRd). Circulating NK cells and CD38+ regulatory T-cells (Tregs) decreased with DRd. The proportion of T-cells increased preferentially in deep responders receiving DRd and correlated with a higher proportion of CD8+ vs CD4+ T-cells. DRd led to a higher proportion of effector memory T-cells vs Rd. In all cells, the phenotype shifted toward CD45RO+ irrespective of the treatment received.
• Krejcik et al (2016)⁴ evaluated the effects of daratumumab on CD38⁺ immune-suppressive subpopulations, T-cell proliferation and activation, and T-cell receptor clonality. Treatment with daratumumab depleted CD38⁺ regulatory T cells, promoted T-cell expansion, and skewed T-cell repertoire.
• Casneuf et al (2016)⁵ assessed the exposure-response relationship of daratumumab and NK cells, and the impact on clinical outcomes of patients with relapsed or refractory multiple myeloma (RRMM) who were treated with daratumumab. CD38 was expressed on NK cells, which were sensitive to treatment with daratumumab. Peripheral NK cells decreased with increasing exposure of daratumumab.
• Cherkasova et al (2015)⁶ treated expanded NK cells with daratumumab F(ab’)2 fragments. Pretreatment protected cells from daratumumab-mediated killing.
• Krejcik et al (2017)⁷ evaluated the effect of daratumumab alone or in combination with Rd, on CD38 levels of MM cells and nontumor immune cells in the GEN501 study (daratumumab monotherapy) and the GEN503 study (daratumumab combined with Rd). In both studies, CD38 expression was reduced on MM cells within hours after starting the first infusion, regardless of depth and duration of response. CD38 expression was also reduced on nontumor immune cells, including NK cells, T cells, B cells, and monocytes, regardless of changes in their absolute numbers during therapy. In addition, daratumumab–CD38 complexes and accompanying cell membrane were actively transferred from MM cells to monocytes and granulocytes. This process of trogocytosis was also associated with reduced surface levels of some other membrane proteins, including CD49d, CD56, and CD138. For streamlining purposes, this has been referenced below.
• Other relevant literature has been identified in addition to the data summarized below.^8-19

product labeling

• CD38 is a transmembrane glycoprotein (48 kDa) expressed on the surface of hematopoietic cells, including clonal plasma cells in multiple myeloma and light chain (AL) amyloidosis, as well as other cell types.² Surface CD38 has multiple functions, including receptor mediated adhesion, signaling, and modulation of cyclase and hydrolase activity.^1,2
• Hyaluronan is a polysaccharide found in the extracellular matrix of the subcutaneous tissue. It is depolymerized by the naturally occurring enzyme hyaluronidase. Unlike the stable structural components of the interstitial matrix, hyaluronan has a half-life of approximately 0.5 days. Hyaluronidase increases permeability of the subcutaneous tissue by depolymerizing hyaluronan. In the doses administered, hyaluronidase in DARZALEX FASPRO acts locally. The effects of hyaluronidase are reversible, and permeability of the subcutaneous tissue is restored within 24 to 48 hours.²

CLINICAL DATA

van de Donk et al (2017)³ explored the ability of daratumumab to promote adaptive T-cell responses and immune changes and investigated the immunophenotype of NK cells that persist upon treatment with Rd or DRd.

Study Design/Methods

• Whole blood samples were collected from patients enrolled in the POLLUX study (a multicenter, randomized, open-label, active-controlled, phase 3 study evaluating the efficacy of DRd vs Rd in patients with RRMM) at baseline (DRd, n=40; Rd, n=45) and after two months of therapy (DRd, n=31; Rd, n=33).
• Samples were stained with a metal-conjugated antibody panel and evaluated via cytometry using a time-of-flight (CyTOF^®) platform.

Results

• Circulating NK cells decreased with DRd.
  • Those that persisted had a distinct phenotype: decreased expression of PD-1 and increased expression of HLA-DR, CD69, CD127 and CD27.
  • These effects were negligible or did not occur with Rd.
• The proportion of T-cells increased preferentially in deep responders receiving DRd (patients with ≥complete response) and correlated with a higher proportion of CD8+ vs CD4+ T-cells.
• In all cells, the phenotype shifted toward CD45RO+ irrespective of the treatment received.
  • Greater increases in HLA-DR expression, particularly for effector memory CD8+ T-cells, occurred in the DRd arm.
• DRd led to a higher proportion of effector memory T-cells vs Rd.
• CD38+ regulatory T-cells (Tregs) were exclusively decreased by DRd.

Krejcik et al (2016)⁴ evaluated the effects of daratumumab on CD38⁺ immune-suppressive subpopulations, T-cell proliferation and activation, and T-cell receptor clonality.

Study Design/Methods

• Peripheral blood and bone marrow from patients with RRMM who were enrolled in 2 daratumumab monotherapy studies (GEN501 [NCT00574288] and SIRIUS [NCT01985126]) were analyzed by flow cytometry, functional assays, and T-cell receptor sequencing before therapy, during therapy, and at relapse (N=148).
  • GEN501 was a phase 1/2 dose escalation (Part 1) and dose-expansion (Part 2) study which included patients with documented multiple myeloma (MM) who had relapsed from or were refractory to ≥2 prior therapies (N=42).
  • SIRIUS was a phase 2 study which included patients who had received ≥3 prior lines of therapy, including a PI and an immunomodulatory agent, or have disease refractory to both a PI and an immunomodulatory agent (N=106).
  • Patients received daratumumab 16 mg/kg in both studies.
• Regulatory B cells and MDSCs were evaluated for immunosuppressive activity and daratumumab sensitivity.

Results

• A new subpopulation of regulatory T cells expressing CD38 was identified (CD4⁺CD25⁺CD127^dim), which were more immunosuppressive in vitro than CD38-negative regulatory T cells and were reduced in patients treated with daratumumab.
• Daratumumab induced increases in helper and cytotoxic T-cell absolute counts.
• In peripheral blood and bone marrow, daratumumab induced significant increases in CD8⁺:CD4⁺ and CD8⁺:regulatory T cell ratios, and increased memory T cells while decreasing naïve T cells.
• Majority of patients had T-cell changes, but patients with a partial response or better in the studies had greater maximum effector and helper T cell increases, increased antiviral and alloreactive functional responses, and significantly greater increases in T-cell clonality as measured by T-cell receptor sequencing.
• Increased T-cell receptor clonality positively correlated with increased CD8⁺ peripheral blood T-cell counts.

Casneuf et al (2016)⁵ assessed the exposure-response relationship of daratumumab and NK cells, and the impact of clinical outcomes of patients with RRMM who were treated with daratumumab.

Study Design/Methods

• ADCC and CDC assays were performed after NK cells isolated from peripheral blood mononuclear cells of healthy donors were treated with daratumumab.
• Samples were pooled from 2 daratumumab monotherapy studies which included patients with RRMM (GEN501, N=104; SIRIUS, N=124).
• After infusion of daratumumab, the kinetics of total NK cells (CD16⁺CD56⁺) and activated NK cells (CD16⁺CD56^dim) were evaluated.
• Associations between changes in NK cells post-treatment with daratumumab and daratumumab exposure, safety, and efficacy were evaluated.

Results

• CD38 was expressed on the surface of NK cells, which made the cells sensitive to daratumumab-mediated ADCC and CDC in vitro.
• After infusion of daratumumab, the numbers of total and activated NK cells were rapidly and significantly reduced in a dose-dependent manner in whole blood and bone marrow of patients, but counts of these cells recovered post-treatment with daratumumab.
• A hyperbolic maximum effect (Emax) dose- or concentration-response relationship was observed for the maximum reduction in peripheral blood NK cells.
• While baseline levels of NK cells (total or activated) between responders and nonresponders were similar, a trend towards higher overall response rate was associated with greater reduction in NK cells following treatment with daratumumab, suggesting that depletion of NK cells did not interfere with the clinical activity of daratumumab.
• No relationships were observed between NK cell reduction during treatment with daratumumab and incidence of grade ≥3 adverse events, infections of any grade, grade ≥3 infections, or herpes zoster.

Cherkasova et al (2015)⁶ treated expanded NK cells with daratumumab F(ab’)2 fragments.

Study Design/Methods

• In vivo, daratumumab was previously found to induce NK cell lymphopenia of unknown etiology.
• NK cells from peripheral blood of healthy volunteers and cancer patients were found to express varying surface levels of CD38.
• In vitro, researchers found that NK cell killing by daratumumab occurred via ADCC.
• In daratumumab-treated patients, the research team blocked CD38 on the surface of NK cells by pretreating them with daratumumab F(ab’)2 fragments to overcome daratumumab-mediated killing of adoptively transferred NK cells.
  • F(ab’)2 fragments were generated using pepsin cleavage of daratumumab and were confirmed to bind and block the CD38 epitope expressed on NK cells.
  • F(ab’)2 fragments remained bound to the surface of NK cells for at least 96 hours, did not induce NK cell apoptosis, protected NK cells from daratumumab-mediated NK cell killing, and bolstered their tumor cytotoxicity against daratumumab-treated myeloma targets.

Results

• In vitro, NK cell tumor cytotoxicity was significantly higher with NK cells that had CD38 blocked with F(ab’)2 fragments vs unblocked myeloma cells in daratumumab-containing media.
• In vivo, pretreatment with daratumumab F(ab’)2 fragments protected human NK cells from daratumumab-mediated killing.
• Compared to untreated NK cell controls, expanded NK cells pretreated with F(ab’)2 fragments prior to adoptive transfer into NOD scid gamma (NSG) mice that had been treated with daratumumab were detectable at significantly higher numbers in the blood.

Literature Search

A literature search of MEDLINE^®, Embase^®, BIOSIS Previews^®, and Derwent Drug File (and/or other resources, including internal/external databases) was conducted on 04 March 2024.