Biotherapeutics are becoming an increasingly common drug class used to treat autoimmune and other inflammatory conditions. Optimization of absorption, distribution, metabolism, and excretion (ADME) profiles of biotherapeutics is crucial for clinical, as well as commercial, success of these drugs. This review focuses on the common questions and challenges in ADME optimization of biotherapeutics for inflammatory conditions. For these immunomodulatory and/or immunosuppressive biotherapeutics, special consideration should be given to the assessment of the interdependency of ADME profiles, pharmacokinetic/pharmacodynamic (PK/PD) relationships, and immunogenicity profiles across various preclinical species and humans, including the interdependencies both in biology and in assay readouts. The context of usage, such as dosing regimens, extent of disease, concomitant medications, and drug product characteristics may have a direct or indirect (via modulation of immunogenicity) impact on ADME profiles of biotherapeutics. Along these lines, emerging topics include assessments of preexisting reactivity to a biotherapeutic agent, impact of immunogenicity on tissue exposure, and analysis of penetration to normal versus inflamed tissues. Because of the above complexities and interdependences, it is essential to interpret PK, PD, and anti-drug antibody results in an integrated manner. In addition, because of the competitive landscape in autoimmune and inflammatory markets, many pioneering ADME-centric protein engineering and subsequent in vivo testing (such as optimization of novel modalities to extend serum and tissue exposures and to improve bioavailability) are being conducted with biotherapeutics in this therapeutic area. However, the ultimate challenge is demonstration of the clinical relevance (or lack thereof) of modified ADME and immunogenicity profiles.

Covalent attachment of poly(ethylene glycol) (PEG) to therapeutic proteins has been used to prolong in vivo exposure of therapeutic proteins. We have examined pharmacokinetic, biodistribution, and biophysical profiles of three different tumor necrosis factor alpha (TNF) Nanobody-40 kDa PEG conjugates: linear 1 × 40 KDa, branched 2 × 20 kDa, and 4 × 10 kDa conjugates. In accord with earlier reports, the superior PK profile was observed for the branched versus linear PEG conjugates, while all three conjugates had similar potency in a cell-based assay. Our results also indicate that (i) a superior PK profile of branched versus linear PEGs is likely to hold across species, (ii) for a given PEG size, the extent of PEG branching affects the PK profile, and (iii) tissue penetration may differ between linear and branched PEG conjugates in a tissue-specific manner. Biophysical analysis (R(g)/R(h) ratio) demonstrated that among the three protein-PEG conjugates the linear PEG conjugate had the most extended time-average conformation and the most exposed surface charges. We hypothesized that these biophysical characteristics of the linear PEG conjugate accounts for relatively less optimal masking of sites involved in elimination of the PEGylated Nanobodies (e.g., intracellular uptake and proteolysis), leading to lower in vivo exposure compared to the branched PEG conjugates. However, additional studies are needed to test this hypothesis.

New classes of CRTH2 antagonists, the pyridazine linker containing indole acetic acids, are described. The initial hit 1 had good potency but poor permeability, metabolic stability, and PK. Initial optimization led to compounds of type 2 with low oxidative metabolism but poor oral bioavailability. Poor permeability was identified as a liability for these compounds. Addition of a linker between the indole and diazine moieties afforded a series with good potency, low rates of metabolism, moderate permeability, and good oral bioavailability in rodents. 32 was identified as the development track candidate. It was potent in cell based, binding, and whole blood assays and exhibited good PK profile. It was efficacious in mouse models of contact hypersensitivity (1 mg/kg b.i.d.) and house dust (20 mg/kg q.d.) when dosed orally. In sheep asthma, administration at 1 mg/kg iv completely blocked the LAR and AHR and attenuated the EAR phase.

Significant progress has been made in understanding pharmacokinetics (PK), pharmacodynamics (PD), as well as toxicity profiles of therapeutic proteins in animals and humans, which have been in commercial development for more than three decades. However, in the PK arena, many fundamental questions remain to be resolved. Investigative and bioanalytical tools need to be established to improve the translation of PK data from animals to humans, and from in vitro assays to in vivo readouts, which would ultimately lead to a higher success rate in drug development. In toxicology, it is known, in general, what studies are needed to safely develop therapeutic proteins, and what studies do not provide relevant information. One of the major complicating factors in nonclinical and clinical programs for therapeutic proteins is the impact of immunogenicity. In this review, we will highlight the emerging science and technology, as well as the challenges around the pharmacokinetic- and safety-related issues in drug development of mAbs and other therapeutic proteins.

We have recently demonstrated that intra-articular (IA) administration of human recombinant lubricin, LUB:1, significantly inhibited cartilage degeneration and pain in the rat meniscal tear model of post-traumatic arthritis. In this report, we show that after a single IA injection to naïve rats and rats that underwent unilateral meniscal tear, [(125)I]LUB:1 had a tri-phasic disposition profile, with the alpha, beta, and gamma half-life estimates of 4.5 h, 1.5 days, and 2.1 weeks, respectively. We hypothesize that the terminal phase kinetics was related to [(125)I]LUB:1 binding to its ligands. [(125)I]LUB:1 was detected on articular cartilage surfaces as long as 28 days after single IA injection. Micro-autoradiography analysis suggested that [(125)I]LUB:1 tended to localize to damaged joint surfaces in rats with meniscal tear. After a single intravenous (IV) dose to rats, [(125)I]LUB:1 was eliminated rapidly from the systemic circulation, with a mean total body clearance of 154 mL/h/kg and a mean elimination half-life (t (1/2)) of 6.7 h. Overall, LUB:1 has met a desired disposition profile of a potential therapeutic intended for an IA administration: target tissue (knee) retention and fast elimination from the systemic circulation after a single IA or IV dose.

Chronic obstructive pulmonary disease (COPD) is an inflammatory lung disease associated with irreversible progressive airflow limitation. Matrix metalloproteinase-12 (MMP-12) has been characterized to be one of the major proteolytic enzymes to induce airway remodeling, destruction of elastin and the aberrant remodeling of damaged alveoli in COPD and asthma. The goal of this project is to develop and identify an orally potent and selective small molecule inhibitor of MMP-12 for treatment of COPD and asthma. Syntheses and structure-activity relationship (SAR) studies of a series of dibenzofuran (DBF) sulfonamides as MMP-12 inhibitors are described. Potent inhibitors of MMP-12 with excellent selectivity against other MMPs were identified. Compound 26 (MMP118), which exhibits excellent oral efficacy in the MMP-12 induced ear-swelling inflammation and lung inflammation mouse models, had been successfully advanced into Development Track status.