A weak association between osmolytes and dihydrofolate (DHF) decreases the affinity of the substrate for the Escherichia coli chromosomal and R67 plasmid dihydrofolate reductase (DHFR) enzymes. To test whether the osmolyte-DHF association also interferes with binding of DHF to FolM, an E. coli enzyme that possesses weak DHFR activity, ligand binding was monitored in the presence of osmolytes. The affinity of FolM for DHF, measured by kcat/Km(DHF), was decreased by the addition of an osmolyte. Additionally, binding of the antifolate drug, methotrexate, to FolM was weakened by the addition of an osmolyte. The changes in ligand binding with water activity were unique for each osmolyte, indicating preferential interaction between the osmolyte and folate and its derivatives; however, additional evidence provided support for further interactions between FolM and osmolytes. Binding of the reduced nicotinamide adenine dinucleotide phosphate (NADPH) cofactor to FolM was monitored by isothermal titration calorimetry as a control for protein-osmolyte association. In the presence of betaine (proposed to be the osmolyte most excluded from protein surfaces), the NADPH Kd decreased, consistent with dehydration effects. However, other osmolytes did not tighten binding to the cofactor. Rather, dimethyl sulfoxide (DMSO) had no effect on the NADPH Kd, while ethylene glycol and polyethylene glycol 400 weakened cofactor binding. Differential scanning calorimetry of FolM in the presence of osmolytes showed that both DMSO and ethylene glycol decreased the stability of FolM, while betaine increased the stability of the protein. These results suggest that some osmolytes can destabilize FolM by preferentially interacting with the protein. Further, these weak attractions can impede ligand binding. These various contributions have to be considered when interpreting osmotic pressure results.

Folate, or vitamin B9, is an important compound in one-carbon metabolism. Previous studies have found weaker binding of dihydrofolate to dihydrofolate reductase in the presence of osmolytes. In other words, osmolytes are more difficult to remove from the dihydrofolate solvation shell than water; this shifts the equilibrium toward the free ligand and protein species. This study uses vapor-pressure osmometry to explore the interaction of folate with the model osmolyte, glycine betaine. This method yields a preferential interaction potential (μ23/RT value). This value is concentration-dependent as folate dimerizes. The μ23/RT value also tracks the deprotonation of folate’s N3–O4 keto–enol group, yielding a pKa of 8.1. To determine which folate atoms interact most strongly with betaine, the interaction of heterocyclic aromatic compounds (as well as other small molecules) with betaine was monitored. Using an accessible surface area approach coupled with osmometry measurements, deconvolution of the μ23/RT values into α values for atom types was achieved. This allows prediction of μ23/RT values for larger molecules such as folate. Molecular dynamics simulations of folate show a variety of structures from extended to L-shaped. These conformers possess μ23/RT values from −0.18 to 0.09 m–1, where a negative value indicates a preference for solvation by betaine and a positive value indicates a preference for water. This range of values is consistent with values observed in osmometry and solubility experiments. As the average predicted folate μ23/RT value is near zero, this indicates folate interacts almost equally well with betaine and water. Specifically, the glutamate tail prefers to interact with water, while the aromatic rings prefer betaine. In general, the more protonated species in our small molecule survey interact better with betaine as they provide a source of hydrogens (betaine is not a hydrogen bond donor). Upon deprotonation of the small molecule, the preference swings toward water interaction because of its hydrogen bond donating capacities.

R67 dihydrofolate reductase (DHFR) is a homotetramer with a single active site pore and no sequence or structural homology with chromosomal DHFRs. The R67 enzyme provides resistance to trimethoprim, an active site-directed inhibitor of Escherichia coli DHFR. Sixteen to twenty N-terminal amino acids are intrinsically disordered in the R67 dimer crystal structure. Chymotrypsin cleavage of 16 N-terminal residues results in an active enzyme with a decreased stability. The space sampled by the disordered N-termini of R67 DHFR was investigated using small angle neutron scattering. From a combined analysis using molecular dynamics and the program SASSIE (), the apoenzyme displays a radius of gyration (Rg) of 21.46 ± 0.50 Å. Addition of glycine betaine, an osmolyte, does not result in folding of the termini as the Rg increases slightly to 22.78 ± 0.87 Å. SASSIE fits of the latter SANS data indicate that the disordered N-termini sample larger regions of space and remain disordered, suggesting they might function as entropic bristles. Pressure perturbation calorimetry also indicated that the volume of R67 DHFR increases upon addition of 10% betaine and decreased at 20% betaine because of the dehydration of the protein. Studies of the hydration of full-length R67 DHFR in the presence of the osmolytes betaine and dimethyl sulfoxide find around 1250 water molecules hydrating the protein. Similar studies with truncated R67 DHFR yield around 400 water molecules hydrating the protein in the presence of betaine. The difference of ∼900 waters indicates the N-termini are well-hydrated.

Monoclonal antibodies (mAbs), while incredibly successful, are prone to a variety of degradation pathways, the most significant of which is aggregation. One of the most commonly used strategy to overcome protein aggregation is addition of excipients to the formulation. Osmolytes such as trehalose, sucrose, and glycine are widely used. In this paper, we explore potential use of naturally occurring osmolytes such as betaine, sarcosine, ectoine, and hydroxyectoine for reducing aggregation of mAb therapeutics. Experimentation has been performed on two IgG1 mAbs via accelerated stability studies. A variety of analytical tools have been used for monitoring the impact, dynamic light scattering (DLS) for colloidal stability, Fourier transform infrared (FTIR) spectroscopy and fluorescence spectroscopy for conformational stability and the higher order structure (HOS), and differential scanning calorimetry (DSC) for thermal stability. No significant impact of osmolyte addition was observed on protein structure, on comparative Fc receptor (FcRn) binding, and on biocompatibility as per our hemolytic assay. Our results rank the osmolytes’ stabilizing trend to be sarcosine > betaine > hydroxyectoine > ectoine. Sarcosine emerged as the most successful osmolyte rendering highest degree of protection against aggregation. Our data support the prospect of using these osmolytes as successful excipients for mAb formulations. Supplementary Information The online version contains supplementary material available at 10.1208/s12249-021-02183-8.

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The stunning rise of biotherapeutics as successful treatments of complex and hard‐to‐treat diseases, in particular cancer, has necessitated the development of a rapid analytical method capable of differentiating these otherwise significantly similar antibody‐based products. The existing methods for product identification pose significant drawbacks in terms of the consumption of time and labor. Here, we present an FTIR spectroscopy‐based simple, rapid, and robust method that is capable of differentiating between the biotherapeutics (both innovator products and biosimilars). The proposed approach uses partial least‐squares‐discriminant analysis to pinpoint subtle differences in the FTIR spectra of the samples, enabling us to not only identify the product but also calculate its concentration. This FTIR‐based method can be used to fulfill the identity testing requirement of a pharmaceutical drug in its final packaged form set by the US Food and Drug Administration. Along with this, identity testing can also be deployed at multiple steps in the manufacturing process and can also be used by the appropriate regulatory or government agency for tackling counterfeits of biotherapeutic products.

No abstract

Bispecific T cell engager (TCE) therapies have exhibited clinical utility against hematological cancers, but limited success in solid tumors. Treatment of solid tumors has additional challenges - including immunosuppressive environments and low T cell infiltration - limiting the antitumor activity of CD3-bispecific TCEs. Conventional T cell activation and sustained proliferation requires signaling via CD3 (signal 1) and costimulatory molecules (signal 2), such as CD28. The balance between signals 1 and 2 is critical for optimal T cell activation – signal 1 in the absence of signal 2 results in T cell anergy, while overactivation via signals 1 and 2 can lead to T cell dysfunction and cytokine release, as observed with toxicities associated with αCD28 superagonist antibodies (Abs). Optimal signal 2 costimulation via CD28 results in improved T cell fitness, activation and proliferation. To improve T cell responses in solid tumors, we developed costimulatory trispecific TCEs (TriTCE Co-stim) that engage CD3, CD28 and a tumor-associated antigen (TAA). Our novel TriTCE Co-stim Abs were generated using the AzymetricTM and EFECTTM platforms to facilitate heterodimeric TriTCE Co-stim assembly and to knockout Fc gamma receptor interactions, respectively. To limit potential CD28-mediated toxicities, we evaluated a conventional αCD28 agonist paratope and generated a paratope library with varying affinities for CD28. TriTCE Co-stim Abs were engineered with various formats, geometries, paratope affinities, and TAA specificities. To understand the impact of TriTCE Co-stim Abs on T cell activation, we assessed in vitro cytotoxicity, cytokine production and proliferation of primary human CD3 T cells in co-culture with TAA-expressing cancer cell lines. A human PBMC-engrafted xenograft model was used to assess in vivo antitumor activity in a TAAhigh tumor model. TriTCE Co-stim Abs exhibited a range of cytotoxic potency, with several formats exhibiting greater potency than bispecific TCEs, and induced greater cytotoxicity of tumor cells in long term co-cultures at low effector to target ratios. TriTCE Co-stim Abs exhibited TAA-dependent cytokine release and T cell proliferation, with enhanced IL-2 production and proliferation compared to that induced by bispecific TCEs. Tumor growth regression was observed in vivo following treatment with different TriTCE Co-stim Ab formats. In summary, we identified TriTCE Co-stim Ab formats that exhibit improved proliferation and antitumor activity against multiple TAA targets compared to bispecific TCE, which may translate to improved and more durable antitumor responses in solid tumors with low T cell infiltration. The evaluation of multiple formats, geometries and paratope affinities allowed optimization of activity and selectivity to promote maximal therapeutic index and efficacy, key factors that may contribute to improved clinical outcomes. Citation Format: Lisa Newhook, Purva P. Bhojane, Peter W. Repenning, Diego Perez Escanda, Nichole K. Escalante, Patricia Zwierzchowski, Alec Robinson, Lauren Clifford, Harsh Pratap, David N. Douda, Chayne L. Piscitelli, Nicole J. Afacan, Thomas Spreter von Kreudenstein, Nina E. Weisser. TriTCE Co-stim, next generation costimulatory trispecific T cell engagers for the treatment of solid tumors. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5121.