Article Figures & Data
Figures
- Fig. 1.
Overview of antibody formats. (A) Schematic representation of the structure of a conventional antibody (Conv. Ab), heavy chain–only antibody (HCAb), and immunoglobulin new antigen receptor (IgNAR). The antibodies consist of constant domains [constant heavy (CH) and constant light (CL)] and variable domains [variable heavy (VH), variable light (VL), variable heavy chain region of a heavy chain–only antibody (VHH), or variable fragment of immunoglobulin new antigen receptor (VNAR)], which make up the Fc region and Fab domains. (B) Overview of commonly used fragments derived from Conv. Abs, HCAbs, or IgNARs. Bispec. Nb, bispecific nanobody; Biv. Nb, bivalent nanobody; Nb, nanobody; Nb-Fc, nanobody-Fc fusion protein; scFv, single-chain variable fragment.
- Fig. 2.
Three-dimensional models of a conventional antibody (left), a nanobody-Fc fusion protein (middle), and a nanobody (right). These models were produced by homology modeling in the software modeler (version 9.15) (Webb and Sali, 2017) and are based on the crystal structure with Protein Data Bank identifier: 1HZH (Saphire et al., 2001) as a template. The sequence of the nanobody corresponds to the Nb VUN400 (Van Hout et al., 2018). CH, constant heavy; CL, constant light; Conv. Ab, conventional antibody; VH, variable heavy; VL, variable light; VHH, variable heavy chain region of a heavy chain–only antibody.
- Fig. 3.
Differences between the reactivity, Kd, or IC50 values of wild-type (WT) and mutant (WT value − mutant value/WT value) reported for 17 CXCR4 antibodies, nanobodies, and antibody-like scaffolds extracted from the literature (Brelot et al., 1999, 2000; Gerlach et al., 2001; Rosenkilde et al., 2004, 2007; Carnec et al., 2005; Jähnichen et al., 2010; Thiele et al., 2014; Griffiths et al., 2016; Peng et al., 2016a; de Wit et al., 2017; Van Hout et al., 2018). The effects are colored for easier interpretation as follows: blue for the less significant effect (reactivity difference 0–0.5, Kd/IC50 difference 0- to 3-fold units), yellow for an intermediate effect (reactivity difference 0.5–0.7, Kd/IC50 difference 3- to 8-fold units), and red for the most significant effects (reactivity difference 0.7–1, Kd/IC50 difference > 8-fold units).
- Fig. 4.
CXCR4 snake plot representations with the most relevant residues involved on the binding of each antibody and antibody-like scaffold (A) or nanobody (B), as indicated in Fig. 3. Snake plots are based on GPCRdb representations (Pándy-Szekeres et al., 2018).
Tables
Antibody Small Molecule General properties Mostly antagonists Antagonists, agonists, and allosteric modulators Preference for extracellular epitopes Binding multiple pockets, including intracellular Administration mostly intravenous or subcutaneous Oral administration possible Immunogenicity minimized by humanization Low risk for immunogenicity Effector functions No effector functions Longer serum half-life, reduced dosing frequency Shorter serum half-life, variable dosing frequency Restricted blood-brain barrier penetration Good blood-brain barrier penetration Development High target expression during immunization and selection needed Development not dependent on target expression Higher costs of development and manufacturing Lower costs of development and manufacturing GPCR targeting Possibility of targeting low-druggability GPCRs Poor tractability, failed to target a variety of GPCRs (e.g., class B2, F) Enhanced selectivity and specificity Lower selectivity, often target family-conserved binding sites Less off-target effects Off-target effects Applications Easy to label and functionalize, e.g., bispecifics, fragments, and conjugates Challenging to label Clinical development Lower overall rate of attrition and higher transition rates at all stages of development Lower approval success rates - TABLE 2
Overview of monoclonal antibodies, nanobodies, and antibody-based fragments and scaffolds directed at and modulating CXCR4 and ACKR3 function
Antibody (Company) Target Format Mechanism of Action Indication Phase Reference Ulocuplumab (Bristol-Myers Squibb) CXCR4 hIgG4 CXCR4 inhibition, apoptosis induction AML Phase 1/2 ongoing (NCT02305563) Kuhne et al. (2013), Kashyap et al. (2016) WM Phase 1/2 ongoing (NCT03225716) LY2624587 (Eli Lilly and Company) CXCR4 hzIgG4 CXCR4 inhibition, apoptosis induction Metastatic cancer Phase 1 completed (NCT01139788) Peng et al. (2016b, 2017) PF-06747143 (Pfizer) CXCR4 hzIgG1 CXCR4 inhibition, apoptosis induction, ADCC, and CDC AML Phase 1 terminated (NCT02954653) Kashyap et al. (2017), Liu et al. (2017), Zhang et al. (2017) hz515H7/F50067 (Pierre Fabre) CXCR4 hzIgG1 CXCR4 inhibition, ADCC, and CDC MM Phase 1 Broussas et al. (2016), Fouquet et al. (2018) MEDI3185 (Medimmune) CXCR4 hIgG1mut CXCR4 inhibition, apoptosis induction Hematologic malignancies Preclinical Kamal et al. (2013), Peng et al. (2016a), Schwickart et al. (2016) IgGX-auristatin CXCR4 IgG, ADC Auristatin-mediated cytotoxicity Metastatic cancer Preclinical Kularatne et al. (2014) 238D2, 238D4 (Ablynx) CXCR4 Nb CXCR4 inhibition, anti-HIV activity, HSC mobilization — Preclinical Jähnichen et al. (2010) 10A10 CXCR4 Nb CXCR4 inhibition WHIM syndrome Preclinical de Wit et al. (2017) VUN400-402 CXCR4 Nb CXCR4 inhibition, anti-HIV activity — Preclinical Van Hout et al. (2018) VUN400-402 CXCR4 Nb-Fc CXCR4 inhibition, anti-HIV activity, ADCC, and CDC — Preclinical Bobkov et al. (2018b) AD-114 (AdAlta) CXCR4 i-body CXCR4 inhibition, anti-HIV activity IPF Preclinical Griffiths et al. (2016, 2018) bAb-AC1, bAb-AC4 CXCR4 Antibody scaffold CXCR4 inhibition — Preclinical Liu et al. (2014) NB1-3 (Ablynx) ACKR3 Nb ACKR3 inhibition Head and neck cancer Preclinical Maussang et al. (2013) X7Ab ACKR3 scFv-Fc ACKR3 inhibition, ADCC, CDC, and ADCP GBM Preclinical Salazar et al. (2018) ADC, antibody-drug conjugate; ADCP, antibody-dependent cellular phagocytosis; AML, acute myeloid leukemia; GBM, glioblastoma; hIgG, human IgG; HSC, hematopoietic stem cell; hzIgG, humanized IgG; IgG1mut, triple mutant lacking ADCC and CDC; IPF, idiopathic pulmonary fibrosis; Nb-Fc, nanobody fused with Fc domain from IgG1; scFv, single-chain variable fragment fused with Fc domain from IgG1; WHIM, warts, hypogammaglobulinemia, infections, and myelokathexis; WM, Waldenström’s macroglobulinemia.
