Tezepelumab anti-TSLP antibody patent analysis

Patent-Disclosed CDR Sequences and SAR Optimisation

Tezepelumab’s six complementarity-determining regions (CDRs), as disclosed in Amgen’s core anti-TSLP patent filings, define the precise molecular grammar of its TSLP binding. The heavy chain carries HCDR1 (GFTFSSYW, SEQ ID NO: 6), HCDR2 (INSQGGST, SEQ ID NO: 7), and HCDR3 (ARSDYDWAWFAY, SEQ ID NO: 8). The light chain carries LCDR1 (QSLLYSSNQKNY, SEQ ID NO: 3), LCDR2 (WAS, SEQ ID NO: 4), and LCDR3 (QQYYRYPPT, SEQ ID NO: 5).

Structure–Activity Relationships Across the CDR Set

The structure–activity relationship (SAR) logic embedded in the CDR sequences is traceable to specific residue-level choices. CDR-H3, at 12 amino acids, is longer than the typical 10–11 residue average and is dominated by aromatic side chains — tryptophan (W), phenylalanine (F), and tyrosine (Y) — that together create a hydrophobic binding pocket capable of deep insertion into the TSLP binding cleft. The arginine (R) and aspartic acid (D) residues in the same loop contribute electrostatic steering and binding specificity.

CDR-L1 (QSLLYSSNQKNY) is similarly extended at 12 amino acids and is rich in polar residues — glutamine (Q), serine (S), asparagine (N), lysine (K), and tyrosine (Y) — providing an extensive hydrogen-bonding network with the TSLP surface. CDR-L3 (QQYYRYPPT) introduces multiple tyrosines for π–π stacking interactions and prolines that impose structural rigidity at the binding interface. The shortest CDR, LCDR2 (WAS), contributes a single tryptophan for hydrophobic contact despite its minimal length.

The full heavy chain variable domain (VH, SEQ ID NO: 10) and light chain variable domain (VL, SEQ ID NO: 12) are built on human germline-derived framework regions, a deliberate choice to minimise immunogenicity risk in a chronic-use therapeutic. The VH is approximately 120 amino acids; the VL, a kappa (κ) type, runs approximately 107–109 amino acids. Encoding polynucleotides are SEQ ID NO: 9 (VH) and SEQ ID NO: 11 (VL).

Epitope Binding Data and TSLP Interaction Mechanism

Tezepelumab recognises a conformational epitope on human TSLP — a binding site assembled from residues that are spatially proximate in the folded cytokine but may be distant in the linear sequence. The target antigen, mature human TSLP, spans amino acids 29–159 of SEQ ID NO: 2 (131 amino acids, ~15 kDa) and adopts a four-helix bundle cytokine fold. Tezepelumab’s binding interface maps to the receptor-recognition surface of this bundle, directly competing with the TSLPR–IL-7Rα heterodimeric receptor complex.

Molecular Interactions at the Binding Interface

The binding interface is characterised by four classes of molecular interaction. Hydrogen bonding is the most extensive: CDR-L1 residues serine, asparagine, and glutamine, together with CDR-H2 asparagine and serine, contribute an estimated 10–15 hydrogen bonds to the TSLP backbone and side chains. Hydrophobic interactions are anchored by the aromatic cluster in CDR-H3 — tryptophan, phenylalanine, and tyrosine — which engage nonpolar TSLP residues and are complemented by the CDR-L2 tryptophan inserting into a hydrophobic pocket on the TSLP surface. Electrostatic interactions include a salt bridge formed by CDR-L1 lysine with acidic TSLP residues, and contributions from CDR-H3 arginine and aspartic acid that provide electrostatic steering. Finally, π–π stacking between CDR-L3 tyrosines and CDR-H3 tryptophan/phenylalanine with aromatic TSLP surface residues further stabilises the complex.

“Tezepelumab’s CDR-H3 aromatic cluster — tryptophan, phenylalanine, and tyrosine in a 12-residue loop — creates a hydrophobic binding pocket that penetrates deeper into the TSLP cleft than the shorter CDR-H3 loops seen in competitor anti-TSLP antibodies.”

Binding affinity is in the subnanomolar range (KD <1 nM), achieved through a rapid association rate (kon: 10⁵–10⁶ M⁻¹s⁻¹) and a slow dissociation rate (koff: 10⁻⁴–10⁻⁵ s⁻¹). The binding stoichiometry disclosed in the patent is 2:1 — two antibody Fab arms can engage one TSLP molecule. According to WIPO‘s patent database, the core anti-TSLP antibody claims covering these CDR sequences and binding characteristics are represented by patents including NZ583933B and ES2581229T3, with active status and expiry estimated around 2028–2030.

Fc Engineering Modifications for Half-Life Extension

Patent WO2022226342A2, filed by Amgen in 2022 and titled “Modified Anti-TSLP antibodies,” discloses Fc engineering strategies designed to extend tezepelumab’s serum half-life beyond the 26–30 days achieved by the unmodified IgG2. The central mechanism is enhanced binding to the neonatal Fc receptor (FcRn) at acidic endosomal pH (pH 6.0) while maintaining reduced binding at physiological pH (pH 7.4) — the pH-dependent cycle that rescues antibodies from lysosomal degradation and returns them to circulation.

Specific Fc Mutation Variants

Three principal Fc variant strategies are described. The YTE variant (M252Y/S254T/T256E) substitutes methionine 252 with tyrosine, serine 254 with threonine, and threonine 256 with glutamic acid, producing a 2–4 fold increase in serum half-life. The LS variant (M428L/N434S) substitutes methionine 428 with leucine and asparagine 434 with serine, producing approximately a 2-fold increase. A triple mutation variant (V259I/V308F/M428L) achieves up to a 4-fold increase in circulation time. All three operate through an optimised FcRn binding interface at endosomal pH.

IgG2 Isotype Selection and Effector Function Minimisation

Before Fc modifications for half-life, the foundational Fc decision was isotype selection. Tezepelumab uses a human IgG2 constant domain (full-length heavy chain: SEQ ID NO: 37 or SEQ ID NO: 105; light chain kappa constant domain: SEQ ID NO: 38 or SEQ ID NO: 106; total molecular weight ~150 kDa). IgG2’s lower affinity for Fcγ receptors (FcγRI, FcγRIIa, FcγRIIIa) produces minimal antibody-dependent cellular cytotoxicity (ADCC) and minimal complement-dependent cytotoxicity (CDC) — appropriate for a neutralising antibody where target cell depletion is not the therapeutic goal and where chronic administration demands a reduced risk of cytokine release syndrome. The IgG2 hinge region’s four inter-heavy chain disulfide bonds, and its dynamic A-form/B-form equilibrium, also reduce aggregation risk and improve structural stability relative to IgG1.

Additional Fc modifications described in the patent include the LALA variant (L234A/L235A), which abolishes C1q binding for complement activation and further reduces FcγR binding. Glycosylation at N297 is maintained for structural stability, with glycoform optimisation preserving the IgG2 effector-silent profile. As documented by EPO filings, these Fc modification claims in WO2022226342A2 extend patent exclusivity to approximately 2042.

Structural Features That Differentiate Tezepelumab from Earlier Anti-TSLP Scaffolds

Tezepelumab’s structural differentiation from competitor anti-TSLP antibodies is visible across four dimensions: CDR-H3 length and composition, CDR-L1 architecture, the aromatic cluster at the binding interface, and IgG2 isotype choice. These are not incremental refinements — they represent a distinct molecular solution to the TSLP neutralisation problem.

The Aromatic Cluster Advantage

The most structurally distinctive feature of tezepelumab is the aromatic cluster formed by HCDR3 (W, F, Y) and LCDR3 (multiple Y residues). This cluster creates a hydrophobic binding pocket with high shape complementarity to the TSLP surface — a binding signature not replicated in earlier anti-TSLP biologic scaffolds, which typically carry shorter CDR-H3 loops of 8–10 amino acids and lack the same density of aromatic residues. Research published by Nature on antibody–cytokine binding interfaces has consistently shown that aromatic-rich paratopes achieve superior shape complementarity with cytokine receptor-binding surfaces, a principle directly embodied in tezepelumab’s CDR design.

Formulation-Level Differentiation

Patent WO2022226339A1 (“Anti-TSLP antibody compositions and uses thereof”) extends structural differentiation into the formulation domain. The high-concentration formulation (100–200 mg/mL tezepelumab) addresses the IgG2-specific aggregation risk from disulfide-mediated hinge region dynamics. Key excipients include histidine or acetate buffer (pH 5.5–6.5), proline at 50–150 mM for structural stabilisation, and polysorbate 80 (0.01–0.05%) for surface adsorption prevention. The patent specifies a critical quality attribute threshold: aspartic acid isomerization derivatives (particularly at the Asp residue in CDR-H3 sequence ARSDYDWAWFAY) must remain below 30% in the final composition, as isomerization can reduce binding affinity by 10–50%. Aggregates must be kept below 5% high molecular weight species, and the shelf life target is 24–36 months at 2–8°C.

Clinical Efficacy and Patent Landscape

Tezepelumab received FDA approval in 2021 for severe asthma, the first anti-TSLP antibody to reach the market. The pivotal NAVIGATOR trial demonstrated a 56% reduction in the annualized asthma exacerbation rate versus placebo, a +0.13 L improvement in pre-bronchodilator FEV1, and decreases in blood eosinophils and FeNO (fractional exhaled nitric oxide). Critically, efficacy was demonstrated across all biomarker subgroups — both eosinophilic and non-eosinophilic asthma — a reflection of TSLP’s position as an upstream initiator of the inflammatory cascade rather than a downstream effector.

Patent Exclusivity Timeline and Biosimilar Implications

The patent estate protecting tezepelumab operates in three layers. Core patents covering CDR sequences, variable domains, and full-length antibody (including NZ583933B and ES2581229T3) are active with expiry estimated around 2028–2030. Fc modification patents (WO2022226342A2) and formulation patents (WO2022226339A1), both filed in 2022, extend exclusivity to approximately 2042. Method-of-use patents (WO2018191479A1, covering dosing regimens and patient populations) add further protection across multiple jurisdictions. Regulatory exclusivity — 12 years in the US, 10 years in the EU — provides an additional layer beyond patent terms. The FDA‘s biosimilar pathway requires demonstrating analytical similarity across all critical quality attributes, including exact CDR sequence replication, IgG2 isoform distribution (A-form/B-form ratio), and equivalent FcRn binding where Fc modifications are present — challenges that make tezepelumab biosimilar development technically demanding even after core patent expiry around 2028–2030. PatSnap’s pharmaceutical intelligence platform tracks these patent families across all jurisdictions in real time. Biosimilar candidates identified include entries from Mabpharm Limited and Qilu Pharmaceutical, with development timelines dependent on the patent expiry cascade described above. Researchers and IP teams can explore the full IP analytics suite to model freedom-to-operate scenarios across these layered protections.