Design and Evaluation of ZD06519, a Novel Camptothecin Payload for Antibody Drug Conjugates.

In recent years, the field of antibody drug conjugates (ADC) has seen a resurgence, largely driven by the clinical benefit observed in patients treated with ADCs incorporating camptothecin-based topoisomerase I inhibitor payloads. Herein, we present the development of a novel camptothecin ZD06519 (FD1), which has been specifically designed for its application as an ADC payload. A panel of camptothecin analogs with different substituents at the C-7 and C-10 positions of the camptothecin core was prepared and tested in vitro. Selected compounds spanning a range of potency and hydrophilicity were elaborated into drug-linkers, conjugated to trastuzumab, and evaluated in vitro and in vivo. ZD06519 was selected on the basis of its favorable properties as a free molecule and as an antibody conjugate, which include moderate free payload potency (∼1 nmol/L), low hydrophobicity, strong bystander activity, robust plasma stability, and high-monomeric ADC content. When conjugated to different antibodies using a clinically validated MC-GGFG-based linker, ZD06519 demonstrated impressive efficacy in multiple cell line-derived xenograft models and noteworthy tolerability in healthy mice, rats, and non-human primates.

Structure-Activity Relationships of Bis-Intercalating Peptides and Their Application as Antibody-Drug Conjugate Payloads.

Synthetic analogs based on the DNA bis-intercalating natural product peptides sandramycin and quinaldopeptin were investigated as antibody drug conjugate (ADC) payloads. Synthesis, biophysical characterization, and in vitro potency of 34 new analogs are described. Conjugation of an initial drug-linker derived from a novel bis-intercalating peptide produced an ADC that was hydrophobic and prone to aggregation. Two strategies were employed to improve ADC physiochemical properties: addition of a solubilizing group in the linker and the use of an enzymatically cleavable hydrophilic mask on the payload itself. All ADCs showed potent in vitro cytotoxicity in high antigen expressing cells; however, masked ADCs were less potent than payload matched unmasked ADCs in lower antigen expressing cell lines. Two pilot in vivo studies were conducted using stochastically conjugated DAR4 anti-FRα ADCs, which showed toxicity even at low doses, and site-specific conjugated (THIOMAB) DAR2 anti-cMet ADCs that were well tolerated and highly efficacious.

Generation and structure-activity relationships of novel imidazo-thienopyridine based TLR7 agonists: application as payloads for immunostimulatory antibody drug-conjugates.

Pairing immunostimulatory small molecules with the targeting capability of an antibody has emerged as a novel therapeutic modality with the potential to treat a variety of solid tumors. A series of compounds based on an imidazo-thienopyridine scaffold were synthesized and tested for their ability to agonize the innate immune sensors toll-like receptor 7 and 8 (TLR7/8). Structure-activity relationship (SAR) studies revealed that certain simple amino-substituents could enable TLR7 agonism at low nanomolar concentrations. Drug-linkers containing either payload 1 or 20h were conjugated to the HER2-targeting antibody trastuzumab at the interchain disulfide cysteine residues using a cleavable valine-citrulline dipeptide linker and stochastic thiol-maleimide chemistry. In vitro, these immune-stimulating antibody drug-conjugates (ADCs) were found to induce cytokine release in a murine splenocyte assay when co-cultured with the HER2-high NCI-N87 cancer cell line. In vivo, tumor regression was observed with a single dose in an NCI-N87 gastric carcinoma xenograft model in BALB/c nude mice.

Effects of the Novel IDO Inhibitor DWG-1036 on the Behavior of Male and Female 3xTg-AD Mice.

The kynurenine pathway metabolizes tryptophan into nicotinamide adenine dinucleotide, producing a number of intermediary metabolites, including 3-hydroxy kynurenine and quinolinic acid, which are involved in the neurodegenerative mechanisms that underlie Alzheimer's disease (AD). Indolamine 2,3-dioxygenase (IDO), the first and rate-limiting enzyme of this pathway, is increased in AD, and it has been hypothesized that blocking this enzyme may slow the progression of AD. In this study, we treated male and female 3xTg-AD and wild-type mice with the novel IDO inhibitor DWG-1036 (80 mg/kg) or vehicle (distilled water) from 2 to 6 months of age and then tested them in a battery of behavioral tests that measured spatial learning and memory (Barnes maze), working memory (trace fear conditioning), motor coordination and learning (rotarod), anxiety (elevated plus maze), and depression (tail suspension test). The 3xTg-AD mice treated with DWG-1036 showed better memory in the trace fear conditioning task and significant improvements in learning but poorer spatial memory in the Barnes maze. DWG-1036 treatment also ameliorated the behaviors associated with increased anxiety in the elevated plus maze and depression-like behaviors in the tail suspension test in 3xTg-AD mice. However, the effects of DWG-1036 treatment on the behavioral tasks were variable, and sex differences were apparent. In addition, high doses of DWG-1036 resulted in reduced body weight, particularly in females. Taken together, our results suggest that the kynurenine pathway is a promising target for treating AD, but more work is needed to determine the effective compounds, examine sex differences, and understand the side effects of the compounds.

Identification of Potent Indoleamine 2,3-Dioxygenase 1 (IDO1) Inhibitors Based on a Phenylimidazole Scaffold.

Inhibition of indoleamine 2,3-dioxygenase (IDO1) is an attractive immunotherapeutic approach for the treatment of a variety of cancers. Dysregulation of this enzyme has also been implicated in other disorders including Alzheimer's disease and arthritis. Herein, we report the structure-based design of two related series of molecules: N1-substituted 5-indoleimidazoles and N1-substituted 5-phenylimidazoles. The latter (and more potent) series was accessed through an unexpected rearrangement of an imine intermediate during a Van Leusen imidazole synthesis reaction. Evidence for the binding modes for both inhibitor series is supported by computational and structure-activity relationship studies.

Diastereoselective tandem reactions of substituted 3-sulfolenes with bis-vinyl ketones leading to highly functionalized bicyclic and tricyclic frameworks.

The base-promoted reaction of 3-sulfolene with bis-vinyl ketones was shown in earlier work to proceed through a γ-1,2 addition/anionic oxy-Cope cascade; a subsequent treatment with base induced a second γ-1,2 addition to provide a [3.3.0] bicyclic framework that our group then exploited in the design of rigidified enzyme inhibitors for influenza neuraminidase. Out of a desire to expand the range of structural archetypes accessible through these couplings (and hopefully access additional conformationally-constrained inhibitor platforms) we have revisited this methodology, this time using substituted starting reagents. We show that judicious choice of the newly added substituent can control the exclusive formation of one of four new structural types, each formed as a single diastereomer. These include bicyclo[3.2.1] sulfones and spiro[5.4] sulfones, as well as an expanded collection of our original bicyclo[3.3.0] sulfone scaffolds, this time incorporating adjacent quaternary centres or additional rings.

Dipolar addition to cyclic vinyl sulfones leading to dual conformation tricycles.

Dipolar addition of cyclic azomethine imines with cyclic vinyl sulfones gave rise to functionalized tricycles that exhibited fluxional behavior in solution at room temperature. The scope of the synthetic methodology was explored, and the origin of the fluxional behavior was probed by NMR methods together with DFT calculations. This behavior was ultimately attributed to stereochemical inversion at one of two nitrogen centers embedded in the tricyclic framework. Two tetracycles were also synthesized, and the degree of signal-broadening in the NMR spectra was found to depend on the presence of substitution next to the inverting nitrogen center.

A rigid bicyclic platform for the generation of conformationally locked neuraminidase inhibitors.

Rapid mutation of the influenza virus through genetic mixing raises the prospect of new strains that are both highly transmissible and highly lethal, and which have the ability to evade both immunization strategies (through mutation of hemagglutinin) and current therapies (through mutation of neuraminidase). Inspired by a need for next-generation therapeutics, a synthetic strategy for a new class of rigid, bicyclic inhibitors of influenza neuraminidase is reported.

The de-guanidinylated derivative of peramivir remains a potent inhibitor of influenza neuraminidase.

The guanidine function in the potent neuraminidase inhibitor peramivir was included early on in the drug design process, and examination of X-ray structural data for the enzyme-inhibitor complex would seem to indicate that the guanidine plays a critical role in promoting binding. However, this functional group may also contribute to the poor oral availability of the drug. Given that the relative stereochemistry on the guanidine-bearing carbon in peramivir is opposite to that in zanamivir (a related neuraminidase inhibitor, for which the guanidine function is known to contribute substantially to the potency), we sought to determine the importance of the guanidine group to peramivir's overall potency. Here we report that the de-guanidinylated analogue of peramivir is only ca. 1-order of magnitude less potent than peramivir itself in two in vitro inhibition assays. This suggests that next-generation inhibitors designed to improve on peramivir's properties might profitably dispense with the guanidine function.

Tandem vinylogous 1,2-addition/anionic oxy-Cope reaction leading from butadiene sulfone to an orthogonally functionalized bicycle.

Here we present a transition metal-free synthesis of a rigid, orthogonally functionalized bicyclic sulfone, starting from readily available reagents. The transformation proceeds via a tandem vinylogous 1,2-addition/anionic oxy-Cope sequence, followed by a second vinylogous ketone addition. Stereochemical assignments suggest that the anionic oxy-Cope reaction proceeds exclusively through a boat-shaped transition state. The product of the two-step sequence can be further functionalized through subsequent chemo- and diastereoselective transformations, suggesting possible applications in medicinal chemistry or materials chemistry.