Dr. Gadek is a medicinal chemist with a Ph.D. from UC Berkeley and 35 years of experience in the Biotechnology and Pharmaceutical industry. He has co-authored more than fifty peer-reviewed journal articles detailing the identification of novel candidates for clinical trials in cardiovascular, metabolic, inflammatory, and auto-immune diseases. He has developed experience and expertise in both the biotech start-up and large pharmaceutical company spaces, guiding the discovery and development of novel chemical entities as both drug substances and drug products, and defining clinical and regulatory strategies which position molecules for clinical and commercial success based on their mechanism of action (MOA) from concept through approval. Most recently Dr. Gadek has focused his efforts in the ocular arena with the discovery and development of Xiidra, leading to its approval by the FDA in 2016. Xiidra’s MOA targets the adhesion, migration, proliferation and inflammatory cytokine release by T-cells as the source of dry eye’s disease pathophysiology. Thus, preclinical MOA was translated into the first agent to demonstrate dose dependent inhibition of both the symptoms and signs of dry eye.
Development of lifitegrast: a novel T-cell inhibitor for the treatment of dry eye disease
Clin Ophthalmol. 2016 Jun 10;10:1083-94. doi: 10.2147/OPTH.S110557. eCollection 2016.
Dry eye disease (DED) is a multifactorial disorder of the ocular surface characterized by symptoms of discomfort, decreased tear quality, and chronic inflammation that affects an estimated 20 million patients in the US alone. DED is associated with localized inflammation of the ocular surface and periocular tissues leading to homing and activation of T cells, cytokine release, and development of hyperosmolar tears. This inflammatory milieu results in symptoms of eye dryness and discomfort. Homing of T cells to the ocular surface is influenced by the binding of lymphocyte function-associated antigen-1 (LFA-1; CD11a/CD18; αLβ2), a cell surface adhesion protein, to its cognate ligand, intercellular adhesion molecule-1 (ICAM-1; CD54), which is expressed on inflamed ocular/periocular epithelium and vascular endothelium. LFA-1/ICAM-1 binding within the immunologic synapse enables both T-cell activation and cytokine release. Lifitegrast is a novel T-cell integrin antagonist that is designed to mimic the binding epitope of ICAM-1. It serves as a molecular decoy to block the binding of LFA-1/ICAM-1 and inhibits the downstream inflammatory process. In vitro studies have demonstrated that lifitegrast inhibits T-cell adhesion to ICAM-1-expressing cells and inhibits secretion of pro-inflammatory cytokines including interferon gamma, tumor necrosis factor alpha, macrophage inflammatory protein 1 alpha, interleukin (IL)-1α, IL-1β, IL-2, IL-4, and IL-6, all of which are known to be associated with DED. Lifitegrast has the potential to be the first pharmaceutical product approved in the US indicated for the treatment of both symptoms and signs of DED. Clinical trials involving over 2,500 adult DED patients have demonstrated that topically administered lifitegrast 5.0% ophthalmic solution can rapidly reduce the symptoms of eye dryness and decrease ocular surface staining with an acceptable long-term safety profile. The purpose of this review is to highlight the developmental story - from bench top to bedside - behind the scientific rationale, engineering, and clinical experience of lifitegrast for the treatment of DED.
Discovery and Development of Potent LFA-1/ICAM-1 Antagonist SAR 1118 as an Ophthalmic Solution for Treating Dry Eye
ACS Med Chem Lett. 2012 Jan 31;3(3):203-6. doi: 10.1021/ml2002482. eCollection 2012 Mar 8.
LFA-1/ICAM-1 interaction is essential in support of inflammatory and specific T-cell regulated immune responses by mediating cell adhesion, leukocyte extravasation, migration, antigen presentation, formation of immunological synapse, and augmentation of T-cell receptor signaling. The increase of ICAM-1 expression levels in conjunctival epithelial cells and acinar cells was observed in animal models and patients diagnosed with dry eye. Therefore, it has been hypothesized that small molecule LFA-1/ICAM-1 antagonists could be an effective topical treatment for dry eye. In this letter, we describe the discovery of a potent tetrahydroisoquinoline (THIQ)-derived LFA-1/ICAM-1 antagonist (SAR 1118) and its development as an ophthalmic solution for treating dry eye.
Corneal inflammation is inhibited by the LFA-1 antagonist, lifitegrast (SAR 1118)
J Ocul Pharmacol Ther. 2013 May;29(4):395-402. doi: 10.1089/jop.2012.0102. Epub 2012 Dec 5.
PURPOSE: Sterile corneal infiltrates can cause pain, blurred vision, and ocular discomfort in silicone hydrogel contact-lens users. The current study investigates the potential for the synthetic lymphocyte functional antigen-1 (LFA-1) antagonist lifitegrast (SAR 1118) to block corneal inflammation using a murine model.
METHODS: The role of LFA-1 (CD11a/CD18) was examined either in CD18(-/-) mice, by intraperitoneal injection of anti-CD11a, or by topical application of lifitegrast. Corneal inflammation was induced by epithelial abrasion and exposure to either tobramycin-killed Pseudomonas aeruginosa or Staphylococcus aureus in the presence of a 2-mm-diameter punch from a silicone hydrogel contact lens. After 24 h, corneal thickness and haze were examined by in vivo confocal microscopy, and neutrophil recruitment to the corneal stroma was detected by immunohistochemistry.
RESULTS: Neutrophil recruitment to the corneal stroma and development of stromal haze were significantly impaired in CD18(-/-) mice or after injection of anti-CD11a. Topical lifitegrast also inhibited P. aeruginosa- and S. aureus-induced inflammation, with the optimal application being a 1% solution applied either 2 or 3 times prior.
CONCLUSION: As LFA-1-dependent neutrophil recruitment to the corneal stroma can be blocked by topical lifitegrast, this reagent could be used in combination with antibiotics to prevent leukocyte infiltration to the corneal stroma in association with contact-lens wear.
Safety and pharmacokinetics of a novel lymphocyte function-associated antigen-1 antagonist ophthalmic solution (SAR 1118) in healthy adults
J Ocul Pharmacol Ther. 2011 Feb;27(1):99-104. doi: 10.1089/jop.2009.0105. Epub 2010 Mar 24.
PURPOSE: To investigate the safety, tolerability, and pharmacokinetics (PKs) of topical SAR 1118 Ophthalmic Solution in healthy adults. SAR 1118 is an investigational small molecule lymphocyte function-associated antigen-1 (LFA-1; CD11a/CD18; αLβ2) antagonist that inhibits LFA-1 binding to intercellular adhesion molecule-1 (ICAM-1; CD54) targeting T-cell-mediated inflammation.
METHODS: A randomized, double-masked, placebo-controlled, dose-escalation study of SAR 1118 was performed in 4 cohorts with 7 randomized subjects per cohort (2 placebo: 5 active drug subjects; 0.1%, 0.3%, 1.0%, 5.0%) in 28 healthy adults. Dosing was divided into 3 periods each separated by a 72-h treatment-free observation: once-daily (QD) × 1, twice-daily (BID) × 10, and thrice-daily (TID) × 10 days. Data obtained at the beginning and end of each period included: slit-lamp, best-corrected visual acuity (BCVA), Schirmer tear test (STT) without anesthesia, tear film break-up time (TBUT), intraocular pressure (IOP), and tear/plasma samples for PK analysis.
RESULTS: All subjects completed the study; there were no tolerability issues or missed treatments (total, 1,428 administered doses). No serious ocular or nonocular adverse events (AEs) occurred over 1,148 subject study days (41 days/subject) and no significant abnormalities were identified on ocular exam. There were 38 ocular AEs (N = 11 subjects) and 21 nonocular AEs (N = 11 subjects). Most AEs were mild in severity and occurred in the 0.3% and placebo groups. No changes were observed in CD3, CD4, and CD8 blood lymphocyte counts. Tear PK profiles support a QD/BID dosing schedule. Plasma levels of SAR 1118 in the 0.1% and 0.3% groups were below level of quantitation (BLQ; <0.50 ng/mL) at all time points and transiently detected within the first 5 min to ∼1 h following administration in the 1.0% and 5.0% groups.
CONCLUSION: SAR 1118 Ophthalmic Solution appears safe and well-tolerated up to 5.0% TID in healthy adult subjects. PK analysis shows adequate ocular exposure with minimal systemic exposure.
Competition between intercellular adhesion molecule-1 and a small-molecule antagonist for a common binding site on the alphal subunit of lymphocyte function-associated antigen-1
Protein Sci. 2006 Feb;15(2):290-303. doi: 10.1110/ps.051583406. Epub 2005 Dec 29.
The lymphocyte function-associated antigen-1 (LFA-1) binding of a unique class of small-molecule antagonists as represented by compound 3 was analyzed in comparison to that of soluble intercellular adhesion molecule-1 (sICAM-1) and A-286982, which respectively define direct and allosteric competitive binding sites within LFA-1's inserted (I) domain. All three molecules antagonized LFA-1 binding to ICAM-1-Immunoglobulin G fusion (ICAM-1-Ig) in a competition ELISA, but only compound 3 and sICAM-1 inhibited the binding of a fluorescein-labeled analog of compound 3 to LFA-1. Compound 3 and sICAM-1 displayed classical direct competitive binding behavior with ICAM-1. Their antagonism of LFA-1 was surmountable by both ICAM-1-Ig and a fluorescein-labeled compound 3 analog. The competition of both sICAM-1 and compound 3 with ICAM-1-Ig for LFA-1 resulted in equivalent and linear Schild plots with slopes of 1.24 and 1.26, respectively. Cross-linking studies with a photoactivated analog of compound 3 localized the high-affinity small-molecule binding site to the N-terminal 507 amino acid segment of the alpha chain of LFA-1, a region that includes the I domain. In addition, cells transfected with a variant of LFA-1 lacking this I domain showed no significant binding of a fluorescein-labeled analog of compound 3 or ICAM-1-Ig. These results demonstrate that compound 3 inhibits the LFA-1/ICAM-1 binding interaction in a directly competitive manner by binding to a high-affinity site on LFA-1. This binding site overlaps with the ICAM-1 binding site on the alpha subunit of LFA-1, which has previously been localized to the I domain.
N-Benzoyl amino acids as ICAM/LFA-1 inhibitors. Part 2: structure-activity relationship of the benzoyl moiety
Bioorg Med Chem Lett. 2004 May 3;14(9):2055-9. doi: 10.1016/j.bmcl.2004.02.046.
o-Bromobenzoyl l-tryptophan 1 inhibits the association of LFA-1 with ICAM-1 with an IC(50) of 1.7microM. Evaluation of the structure-activity relationship of the benzoyl moiety shows that 2,6-di-substitutions greatly enhance potency of this class of inhibitors. Electronegative substitutions that favor a 90 degrees angle between the benzoyl ring and the amide bond yield the most potent compounds. There is a strong correlation between the potency of the compounds and the difference between the ab initio energy at 90 degrees and the global minima energy for given compounds. Combining the favored benzoyl substitutions with l-histidine and l-asparagine resulted in a 15-fold increase in potency over compound 1.
Discovery of novel PTP1b inhibitors
Bioorg Med Chem Lett. 2004 Jan 19;14(2):389-91. doi: 10.1016/j.bmcl.2003.10.058.
A small library of 19 compounds was designed based on unique structural features of PTP1b. Utilizing electrospray ionization mass spectrometry (ESI-MS) to provide binding information about complexes of enzyme and small molecule ligands, two classes of lead compounds were discovered.
Structure-activity relationships by mass spectrometry: identification of novel MMP-3 inhibitors
Bioorg Med Chem. 2004 Jan 2;12(1):37-44. doi: 10.1016/j.bmc.2003.10.053.
A novel class of nonpeptide inhibitors of stromelysin (MMP-3) has been discovered with the use of mass spectrometry. The method relies on the development of structure-activity relationships by mass spectrometry (SAR by MS) and utilizes information derived from the binding of known inhibitors to identify novel inhibitors of a target protein with a minimum of synthetic effort. Noncovalent complexes of known inhibitors with a target protein are analyzed; these inhibitors are deconstructed into sets of fragments which compete for common or overlapping binding sites on the target protein. The binding of each fragment set can be studied independently. With the use of competition studies, novel members of each fragment set are identified from compound libraries that bind to the same site on the target protein. A novel inhibitor of the target protein was then constructed by chemically linking a combination of members of each fragment set in a manner guided by the proximity and orientation of the fragments derived from the known inhibitors. In the case of stromelysin, a novel inhibitor composed of favorably linked fragments was observed to form a 1:1 complex with stromelysin. Compounds that were not linked appropriately formed higher order complexes with stoichiometries of 2:1 or greater. These linked molecules were subsequently assessed for their ability to block stromelysin function in a chromogenic substrate assay.
Discovery of small molecule leads in a biotechnology datastream
Drug Discov Today. 2003 Jun 15;8(12):545-50. doi: 10.1016/s1359-6446(03)02735-1.
A case study of the discovery of small molecule antagonists to the integrins GPIIbIIIa (alphaII(B)beta3), alphavbeta3, LFA-1 (alphaLbeta2), alpha4beta1 and alpha4beta7 is presented from the perspective of a biotechnology research organization. A strategy incorporating protein mutagenesis and structural studies to develop a structure-activity relationship (SAR) that described the 'epitope' of the integrin ligand was crucial to the identification of peptide analogs of these proteins, and subsequently, through parallel trends in SAR, to the identification of small molecule mimetics of these peptides, which are active analogs of the protein ligands themselves.
Strategies and methods in the identification of antagonists of protein-protein interactions
Biotechniques. 2003 Jun;Suppl:21-4.
The identification of antagonists of protein-protein interactions is a critical challenge to the pharmaceutical industry. The selection of a protein target, which is amenable to antagonism, is the first of many decisions that determine the success of these efforts. In addition, the definition of strategies and the development and application of methodologies appropriate to that target will be vital to the success of efforts to identify antagonists of a protein-protein interaction. An analysis of current approaches to the identification of lead molecules demonstrates that a search for competitors of a known binder is the basis of traditional screening as well as more modern approaches based on structure activity relationship (SAR) by nuclear magnetic resonance (NMR), molecular fragments, rational design, and tethering. The latter methods employ a structural perspective, throughout the discovery and optimization of a lead, to provide the practitioner with some control over the success of the process.
N-Benzoyl amino acids as LFA-1/ICAM inhibitors 1: amino acid structure-activity relationship
Bioorg Med Chem Lett. 2003 Mar 24;13(6):1015-8. doi: 10.1016/s0960-894x(03)00084-2.
The association of ICAM-1 with LFA-1 plays a critical role in several autoimmune diseases. N-2-Bromobenzoyl L-tryptophan, compound 1, was identified as an inhibitor to the formation of the LFA-1/ICAM complex. The SAR of the amino acid indicates that the carboxylic acid is required for inhibition and that L-histidine is the most favored amino acid.
Small molecule antagonists of proteins
Biochem Pharmacol. 2003 Jan 1;65(1):1-8. doi: 10.1016/s0006-2952(02)01479-x.
The identification of small molecule antagonists of protein function is at the core of the pharmaceutical industry. Successful approaches to this problem, including screening and rational design, have been developed over the years to identify antagonists of enzymes and cellular receptors. These methods have been extended to the search for inhibitors of protein-protein interactions. While the very possibility of designing a small molecule inhibitor for such interactions was once doubted, there are examples of such inhibitors that are currently marketed products and many more inhibitors in various stages of research and development. Here we review the progress in identifying and designing small molecule protein inhibitors, with particular attention to those that block protein-protein interactions. We also discuss the physical character of protein-protein interfaces, and the resulting implications for small molecule lead discovery and design.