Discovery of ABBV-154, an anti-TNF Glucocorticoid Receptor Modulator Immunology Antibody-Drug Conjugate (iADC)

Stable attachment of drug-linkers to the antibody is a critical requirement, and for maleimide conjugation to cysteine, it is achieved by ring hydrolysis of the succinimide ring. During ADC profiling in our in-house property screening funnel, we discovered that the succinimide ring open form is in equilibrium with the ring closed succinimide. Bromoacetamide (BrAc) was identified as the optimal replacement, as it affords stable attachment of the drug-linker to the antibody while completely removing the undesired ring open-closed equilibrium. Additionally, BrAc also offers multiple benefits over maleimide, especially with respect to homogeneity of the ADC structure. In combination with a short, hydrophilic linker and phosphate prodrug on the payload, this afforded a stable ADC (ABBV-154) with the desired properties to enable long-term stability to facilitate subcutaneous self-administration.

Optimization of Drug-Linker to Enable Long-term Storage of Antibody-Drug Conjugate for Subcutaneous Dosing

To facilitate subcutaneous dosing, biotherapeutics need to exhibit properties that enable high-concentration formulation and long-term stability in the formulation buffer. For antibody-drug conjugates (ADCs), the introduction of drug-linkers can lead to increased hydrophobicity and higher levels of aggregation, which are both detrimental to the properties required for subcutaneous dosing. Herein we show how the physicochemical properties of ADCs could be controlled through the drug-linker chemistry in combination with prodrug chemistry of the payload, and how optimization of these combinations could afford ADCs with significantly improved solution stability. Key to achieving this optimization is the use of an accelerated stress test performed in a minimal formulation buffer.

Discovery of ABBV-3373, an Anti-TNF Glucocorticoid Receptor Modulator Immunology Antibody Drug Conjugate

Using a convergent synthetic route to enable multiple points of diversity, a series of glucocorticoid receptor modulators (GRM) were profiled for potency, selectivity, and drug-like properties in vitro. Despite covering a large range of diversity, profiling the nonconjugated small molecule was suboptimal and they were conjugated to a mouse antitumor necrosis factor (TNF) antibody using the MP-Ala-Ala linker. Screening of the resulting antibody drug conjugates (ADCs) provided a better assessment of efficacy and physical properties, reinforcing the need to conduct structure-activity relationship studies on the complete ADC. DAR4 ADCs were screened in an acute mouse contact hypersensitivity model measuring biomarkers to ensure a sufficient therapeutic window. In a chronic mouse arthritis model, mouse anti-TNF GRM ADCs were efficacious after a single dose of 10 mg/kg i.p. for over 30 days. Data on the unconjugated payloads and mouse surrogate anti-TNF ADCs identified payload 17 which was conjugated to a human anti-TNF antibody and advanced to the clinic as ABBV-3373.

Design and Development of Glucocorticoid Receptor Modulators as Immunology Antibody-Drug Conjugate Payloads

Glucocorticoid receptor modulators (GRM) are the first-line treatment for many immune diseases, but unwanted side effects restrict chronic dosing. However, targeted delivery of a GRM payload via an immunology antibody-drug conjugate (iADC) may deliver significant efficacy at doses that do not lead to unwanted side effects. We initiated our α-TNF-GRM ADC project focusing on identifying the optimal payload and a linker that afforded stable attachment to both the payload and antibody, resulting in the identification of the synthetically accessible maleimide-Gly-Ala-Ala linker. DAR 4 purified ADCs were shown to be more efficacious in a mouse contact hypersensitivity model than the parent α-TNF antibody. Analysis of P1NP and corticosterone biomarkers showed there was a sufficient therapeutic window between efficacy and unwanted effects. In a chronic mouse arthritis model, α-TNF-GRM ADCs were more efficacious than both the parent α-TNF mAb and an isotype control bearing the same GRM payload.

Expression of antibodies using single open reading frame (sORF) vector design: Demonstration of manufacturing feasibility

Efficient production of large quantities of therapeutic antibodies is becoming a major goal of the pharmaceutical industry. We developed a proprietary expression system using a polyprotein precursor-based approach to antibody expression in mammalian cells. In this approach, the coding regions for heavy and light chains are included within a single open reading frame (sORF) separated by an in-frame intein gene. A single mRNA and subsequent polypeptide are produced upon transient and stable transfection into HEK293 and CHO cells, respectively. Heavy and light chains are separated by the autocatalytic action of the intein and antibody processing proceeds to produce active, secreted antibody. Here, we report advances in sORF technology toward establishment of a viable manufacturing platform for therapeutic antibodies in CHO cells. Increasing expression levels and improving antibody processing by intein and signal peptide selection are discussed.

Characterization of maleuric acid derivatives on transgenic human monoclonal antibody due to post-secretional modifications in goat milk

A fully human antibody to tumor necrosis factor-alpha was expressed in the mammary glands of transgenic goats. The goat expressed antibody (gAb) is heterogeneous and has several isoforms due to typical cellular post-translational modifications. In addition, one post-secretional modification on gAb was discovered by high-resolution cation exchange chromatography (CIEX). The presence of these variants in the final product was shown to be dependent upon the initial milk storage and traditional purification methodologies used. These observations allow for the development of new sample recovery and purification processes to eliminate these variants. Various enzymatic treatments were used to characterize different gAb heavy chain C-terminal lysine and sialic acid variants. In addition, an unknown derivative with the additional mass of 140 Da was found in transgenic gAb using mass spectrometry (MS). The modification sites were identified as the N-termini of gAb light chains and heavy chains using Q-TOF MS. Characterization of transgenic gAb isoforms was facilitated by utilizing different enzymes, CIEX and MS techniques. A maleuric acid modification on the N-terminal portion of gAb was shown to be consistent with the available data characterizing this new derivative of transgenic gAb isoforms in goat milk.

Characterization of noncovalent complexes of recombinant human monoclonal antibody and antigen using cation exchange, size exclusion chromatography, and BIAcore

The binding of fully human monoclonal antibodies (MAbs) D2E7 and 2SD4 to their antigen, human tumor necrosis factor-alpha (TNFalpha), was investigated by BIAcore, cation exchange (CIEX), and size exclusion liquid chromatography (SEC) using ultraviolet and laser light scattering detectors. D2E7 has a higher affinity for TNFalpha than 2SD4 and the two antibodies (Abs) differ by 12 amino acids in the antigen (Ag) binding regions. A BIAcore biosensor instrument was used to determine the association, k(on) and dissociation, k(off), rate constants for the binding of TNFalpha to D2E7 and 2SD4. The HPLC methods were used to resolve and to study D2E7, 2SD4, and TNFalpha molecules and the noncovalent complexes of D2E7 and 2SD4 with TNFalpha. The CIEX method demonstrated that all D2E7 charged-variants bound TNFalpha equally well. There was no preferential binding for any one of D2E7 charged-variants to TNFalpha. D2E7 and 2SD4 Abs were resolved by the CIEX method. When a mixture of D2E7 and 2SD4 was mixed with excess TNFalpha, D2E7. TNFalpha complexes were formed before any 2SD4. TNFalpha complexes. Thus, the CIEX method was able to rank the affinities of the MAbs. D2E7 and TNFalpha formed complexes of 600-5000 kDa. The molecular weights of various D2E7. TNFalpha complexes were determined by a SEC method with light scattering (LS) and refractive index (RI) detectors. Upon overnight incubation, a 598-kDa complex emerged as the most stable and the only D2E7. TNFalpha complex. The molar ratio of D2E7 to TNFalpha in this complex was approximately 1:1. Based on molecular weights and the molar ratio, an immune complex, consisting of alternating three D2E7 and three TNFalpha molecules, is proposed as the most stable complex.

Characterization of recombinant human monoclonal tissue necrosis factor-alpha antibody using cation-exchange HPLC and capillary isoelectric focusing

Cation-exchange liquid chromatography (CIEX) and capillary isoelectric focusing (cIEF) methods have been developed for the routine analysis of a recombinant, human anti-tumor necrosis factor monoclonal antibody D2E7. Both of these methods can separate heavy-chain C-terminal variants of this antibody. Various enzymatic digestion methods have also been developed for the identification of the antibody C-termini lysine (Lys) variants. A comparison of conventional CIEX-HPLC and cIEF methods has been made for the analysis of antibodies. cIEF can also be used to determine the isoelectric points (pI) of antibody variants based on the use of internal pI standards. Different C-termini Lys variants have been separated and collected from the CIEX column and subsequently analyzed by cIEF and mass spectrometry.