Abstract by by Khaled Mohamed Elhady Hussin Yousry Mohamed

Metabolic-related conditions are rising rapidly worldwide, with the obese population reaching over 1 billion by 2030. Obesity is a common risk factor for cardiovascular diseases, diabetes, cancer, and musculoskeletal disorders. Although musculoskeletal disorders like osteoarthritis trouble healthcare systems and patients, osteoarthritis remains without an approved treatment. Osteoarthritis (OA) is among the top causes of disability, with pain as the most detrimental cause to patients’ quality of life. Recent failures in OA drug development highlight the need for better-suited preclinical models. Even though obesity and weight loss are integral to OA’s pathology and management, the metabolic element is underrepresented in OA preclinical drug development. Treatment options offering an anti-obesity effect with joint structural preservation have a better opportunity of becoming disease-modifying osteoarthritis drugs (DMOADs). In addition to pain relief, structural improvement is an essential aspect of OA treatment. Dual amylin and calcitonin receptor agonists (DACRAs) combine proven metabolic effects through weight loss with potential structural preservation capabilities primarily through inhibition of bone remodeling. Recently developed DACRAs like KeyBioscience Peptides (KBPs) possess potent efficacy on calcitonin and amylin receptors in vitro and in vivo. Considering KBPs’ vast metabolic benefits and proven effectiveness on pain and structure in a lean OA preclinical model, an obese OA model will be a valuable tool for evaluating the potential disease-modifying effects of KBP.

The aims of this thesis are first to investigate the relationship between obesity and OA, shedding more light on the painful experience in humans through an obese preclinical model of OA. Second, testing the long-acting DACRA KBP-336 on the metabolic OA model by evaluating its effect mainly on pain and structure. The final aim of this thesis is to understand which of the two receptors that mediate the pain-alleviating outcomes of KBP by comparing a selective long-acting ligand with KBP on the metabolic OA model.

We analyzed clinical data from a previous phase III clinical trial on OA by studying the relationship between body mass index (BMI) and the total WOMAC scores for OA pain at the start of the study and then examined the effect of a 5% loss or gain in body weight on the WOMAC scores two years after the beginning of the study. Aiming to represent obesity in our preclinical OA model, Sprague Dawley (SD) rats were fed a normal diet (ND) or a high-fat diet (HFD). Mechanical allodynia was assessed using von Frey tests to gauge the nociceptive experience pre-OA induction. Unilateral medial meniscectomy surgery was used to induce OA. After OA induction, nociceptive behavior was monitored using von Frey, and cartilage damage was measured at the study end by scoring histological sections (OA score). Using this preclinical metabolic OA model, the effect of KBP-336 on mechanical allodynia and cartilage structure was investigated. Upon focusing on the painful experience, the impact of KBP on pain-like symptoms was examined in male and female SD rats. After studying the selectivity of a presumed selective acylated human calcitonin (hCTA), hCTA was tested on the animal model to compare its effect on pain-like symptoms with KBP-336.

In OA patients, at the beginning of the clinical trial, the total WOMAC scores were higher with increased BMI. After two years, patients who lost 5% or more body weight had better WOMAC function scores and tended to have better total WOMAC scores than those who lost or gained less than 5% body weight. In rats, animals on HFD experienced sensitization with a lower 50% paw withdrawal threshold (PWT) during the first 40 days compared to the ND group. After OA induction, MNX groups exhibited lower PWT throughout the study than the sham groups. A two-way ANOVA statistical analysis of the net AUC showed HFD and MNX as significant factors affecting the mechanical allodynia displayed. Upon examining the OA scores, MNX groups showed more damage than sham groups. Further statistical analysis revealed a considerable diet effect with the MNX surgery on the OA scores. Obesity and weight loss played a critical role in fueling and relieving OA pain in patients. This role is reflected in the preclinical model, as the nociceptive experienced was amplified after adding the metabolic element.

KBP-336 was tested in the metabolic OA model in female SD rats. The KBP-treated group had higher PWT than the vehicle-treated MNX group throughout and until the end of the study. Structurally, the KBP group did not improve their OA score compared to the vehicle-treated MNX group. Metabolically, KBP-treated animals experienced significant weight loss compared to the vehicle-treated groups, which they maintained until the end of the study. The weight loss was reflected in the smaller inguinal and perirenal fatty tissues of the KBP group compared to the vehicle groups. KBP’s effect on mechanical allodynia was observed in male rats, as KBP-treated male rats had higher PWT than the MNX vehicle-treated group. Overall, KBP-336 produced higher PWT, improving mechanical allodynia in a metabolic model of OA in female and male rats.

The influence of the calcitonin receptor on the pain-alleviating effects of KBP was revealed by comparing KBP at three different doses with hCTA in the metabolic OA model. The three KBP doses and hCTA increased the PWT compared to the vehicle during and at the study end. The group treated with the lowest dose of KBP-336 had higher PWT than the vehicle-treated MNX, with little to no effect on weight and adipose tissues. hCTA did not affect food intake or fat tissue masses, indicating the lack of amylin receptor activation. On the other hand, in an acute study, after one injection of hCTA at different doses, the release of CTX-I was inhibited, confirming calcitonin receptor activation. These findings demonstrate the importance of calcitonin receptor activation in the pain-alleviating effects of DACRAs, particularly KBPs.

In conclusion, obesity fuels OA pain in patients, which makes weight loss a crucial aspect of OA management. Obese individuals experienced more OA pain than nonobese ones. Losing 5% or more of weight helped patients feel less pain than patients who lost or gained less than 5% of body weight. Including a metabolic element in preclinical models supports the development of a successful DMOAD. Obesity augmented the pain and cartilage damage in the metabolic OA model. KBP-336 alleviated the pain-like symptoms while no effect was detected on cartilage damage. Independent of body weight, the long-acting calcitonin hCTA improved nociception as well as KBP treatment, indicating the vital role of the calcitonin receptor activity in the pain-alleviating effects of KBP.