LRP6

Low density lipoprotein receptor-associated protein 5/6 (LRP5/6) forms a complex with Wnt protein that triggers cytoplasmic tail phosphorylation of LRP5 or LRP6, which in turn causes Axin to bind to it and inhibit the activity of glycogen synthase kinase (GSK-3β). This process leads to increased phosphorylation of β-catenin, promotes its nuclear translocation, forms complexes with DNA-binding proteins, activates target gene promoters, and ultimately promotes differentiation, proliferation, and survival of osteoblasts. Studies have revealed that Sclerostin secreted by Osteocytes (Osteocytes) interferes with Wnt signaling and stabilizes β-catenin by competitively binding LRP5/6, thus reducing osteogenic activity and triggering osteoporosis. Therefore, blocking the interaction between sclerotin and LRP5/6 can enhance Wnt signaling, increase bone formation, and inhibit bone resorption. By specifically binding to osteosin, osteosinomumab reduces its inhibition of Wnt signaling pathway, thereby promoting osteogenesis and inhibiting osteoclast, and realizing dual mechanism therapy for osteoporosis. Currently, only one drug that targets SOST, Romozolzumab, has been approved for marketing. Romosozumab is the first humanized IgG2 monoclonal antibody targeting SOST osteosclerosis protein, but its road to market has been challenging. In 2017, the FDA rejected romosozumab's U.S. marketing application, citing concerns about an increased risk of cardiovascular events in patients. Subsequently, Amgen and UCB provided additional Phase III clinical data at the FDA request, which was not approved until April 2023. However, the EU CHMP rejected romosozumab's marketing application in June of the same year due to cardiovascular risk concerns, which also limited its projected 2024 sales to only $3.2 billion. Setrusumab is the world's second SOST monoclonal antibody for the treatment of osteogenesis imperfecta (OI). OI is a rare genetic bone disorder characterized by low bone mass and fragility fractures. Setrusumab is a fully human IgG2 monoclonal antibody that treats OI by inhibiting the function of sclerosin, a protein that inhibits the activity of osteoblasts. In June, Ultragenyx Pharmaceutical and Mereo BioPharma announced that setrusumab showed significant results in a sustained reduction in fracture rates in Orbit, the Phase 2 portion of a 2/3 clinical trial for OI patients. Blosozumab is a humanized monoclonal antibody against osteosin developed by Eli Lilly for the treatment of osteoporosis. The company is licensed to develop and commercialize Blosozumab in Greater China. Lilly completed Phase II clinical trials in the United States and Japan, showing favorable safety and efficacy. In May 2023, Transom Group announced Phase I data showing that TST002 (Blosozumab) demonstrated a good safety and tolerability profile in all dose groups, and demonstrated a clinically significant increase in lumbar bone density in terms of efficacy. SHR-1222, China's first SOST monoclonal antibody developed by Hengrui Pharmaceutical, is currently in Phase I clinical trials. Osteoporosis is a systemic bone disease characterized by loss of bone mass and destruction of bone microstructure, resulting in increased bone fragility and susceptibility to fracture. With an aging population, China has the largest number of osteoporosis patients, with about 90 million patients, accounting for 7 percent of the total population, and at least 210 million people with lower than normal bone mass. Therefore, the market potential of osteoporosis treatment drugs is huge. The market size of osteoporosis drugs in China is expected to reach 36.8 billion yuan in 2025 and further grow to 51.2 billion yuan in 2030. The sclerotinomumab represented by Romozomumab provides a new strategy for the treatment of osteoporosis, which is expected to overcome the limitations of traditional drugs and become the focus of future research and treatment.

Bispecific antibodies (bsAbs) possess unique advantages due to their ability to simultaneously target two distinct antigens, which helps to enhance the immune system's recognition and killing of tumor cells. As of the end of 2023, 14 bsAbs have been approved: 11 of them for cancer treatment and 3 for non-oncological indications. BsAbs come in various structural formats, target different antigens, and mediate antitumor functions through different molecular mechanisms. The development of antibodies targeting G protein-coupled receptor (GPCR) targets is relatively more challenging compared to traditional drugs such as small molecules, peptides, recombinant hormones, etc., with slower progress in comparison. In contrast, the development of Antibody-Drug Conjugates (ADCs) targeting members of the GPCR family has seen a gradual increase in research momentum over the past decade. Dual-specificity antibodies related to GPCRAccording to statistics from the Synapse database, there are currently 23 bispecific antibody therapeutics worldwide targeting GPCR (G protein-coupled receptor) class targets, including targets such as CXCR4 (+PD-L1) , GPRC5D (+CD3) , GPRC5D (+BCMA+CD30) , SSTR2 (+CD3) , ETA (+CD3) , ETA (+TGF-B) , CCR8 (+TIGIT) , CCR8 (+CTLA4) , CCR2 (+M-CSF) , FZD5 (+LRP6) , FZD4 (+LRP5), GIPR+GLP-1R, FSHR (+albumin) , LGR5 (+EGFR). Johnson & Johnson's Talquetamab became the world's first approved bispecific antibody targeting a GPCR class target to be marketed. Bispecific antibodies that target both GPRC5D and CD3 include Nanjing Leads Biolabs' LBL-034, which is in Phase 1/2 clinical trials, and Roche's Forimtamig, which is in Phase 1 clinical development. Additionally, the GPRC5D+CD3+BCMA trispecific antibody MBS314, co-developed by Kyinno Biotechnology and Beijing Mabworks Biotech, is in Phase 1/2 clinical trials, and the GPRC5D+CD3+BCMA trispecific antibody SIM-0500, co-developed by Simcere Pharmaceutical Group Limited and Shanghai Xianxiang Pharmaceutical Technology, is in the clinical application stage. Translate the following text into English with professional accuracy: The Dutch biotechnology company Merus has developed a bispecific product, Petosemtamab (MCLA-158), currently in Phase 1/2 clinical trials. This is a bispecific Biclonics® fucose-low full human IgG1 antibody that simultaneously targets the epidermal growth factor receptor (EGFR) and leucine-rich repeat-containing G-protein coupled receptor 5 (LGR5). Petosemtamab is designed with three independent mechanisms of action: Inhibition of the EGFR-dependent signaling pathway: By binding with EGFR on the surface of tumor cells, it blocks normal signal transmission, thereby inhibiting processes such as tumor cell proliferation, migration, and angiogenesis.  LGR5-mediated EGFR internalization and degradation: Petosemtamab can bind to LGR5, leading to the internalization and degradation of EGFR within cancer cells, further diminishing EGFR’s pro-carcinogenic activity.  Enhancement of antibody-dependent cellular cytotoxicity and phagocytosis (ADCC/ADCP): With its bispecific structure, Petosemtamab can recruit and activate the immune system's natural killer (NK) cells and macrophages, enhancing their ability to recognize and eliminate cancer cells expressing EGFR and LGR5, thus achieving indirect antitumor effects. At the 2023 Annual Meeting of the American Association for Cancer Research (AACR), Merus presented the results of a Phase 1/2 clinical trial cohort expansion, showing that Petosemtamab demonstrated a manageable safety profile and significant therapeutic effects in patients with advanced head and neck squamous cell carcinoma (HNSCC). Among the 43 patients with advanced HNSCC treated with Petosemtamab, the overall response rate (ORR) reached 37.2%, with tumor reductions observed in 16 patients. The data specifics included: 1 patient achieved a complete response (CR), and 15 patients had partial responses (PR). In addition, 15 patients achieved a stable disease (SD) condition. As a result, the disease control rate (DCR) was 72.1% (n=31/43; 95% CI, 56.3%-84.7%), which means that over seventy percent of the patients experienced no tumor progression or saw reductions in tumor size following treatment. The bi-specific product SZN-1326, originally developed by the American biotechnology company Surrozen, is in Phase 1 clinical research. The product is designed based on Surrozen's proprietary SWAP™ technology, with the goal of modulating the Wnt signaling pathway in intestinal epithelium. The Wnt/β-catenin signaling pathway plays a crucial role in the renewal of intestinal stem cells, the maintenance of intestinal epithelial homeostasis, and the regeneration process. Studies have confirmed that this pathway is dysregulated in inflammatory bowel disease (IBD). Fzd5 is a Wnt receptor with high expression in intestinal epithelial tissues. SZN-1326 is a bi-specific, effectorless IgG1 antibody that targets both FZD5 and 8, as well as the LRP6 receptor. Preclinical research has indicated that SZN-1326 can effectively activate the Wnt signaling pathway. Furthermore, in organoid cultures of the intestine, it can stimulate the growth of the organoids; it increases the expression levels of the Wnt target gene Axin2 in colonic tissue; and in a mouse model, SZN-1326 can also ameliorate colitis symptoms induced by Dextran Sulfate Sodium (DSS). At present, bispecific antibodies targeting GPCR class targets are primarily indicated for cancer-related clinical applications, with popular therapeutic directions including multiple myeloma, plasma cell myeloma, solid tumors, and more. However, there is also a diversity of clinical indications, such as bispecific antibodies targeting GIPR and GLP-1R for the treatment of obesity and diabetes, bispecific antibodies targeting ETA for the treatment of pulmonary fibrosis and pulmonary arterial hypertension, bispecific antibodies targeting FSHR for the treatment of male/female infertility, and bispecific antibodies targeting FZD4 for the treatment of diabetic retinopathy and wet age-related macular degeneration.

Surrozen announced it will stop developing SZN-1326 for inflammatory bowel disease (IBD) after running into challenges finding a safe and effective dose in a Phase I trial. The news shaved off about 4% of its stock price on Thursday.The bi-specific antibody modulates Wnt signaling in target tissue by binding to particular Frizzled and LRP receptors that are highly expressed in intestinal crypts. Surrozen has said that SZN-1326 demonstrated repair of damaged intestinal epithelium and anti-inflammatory effects in preclinical models.Elevated transaminase levelsSurrozen's decision to drop the IBD programme follows the completion of a Phase I single ascending dose trial involving 37 healthy volunteers. The company said it struggled to identify an ideal dose of the drug after several participants at higher dose levels experienced asymptomatic liver enzyme increases, including four who had Grade 3 ALT and AST elevations.There were no other clinically significant lab abnormalities, and the transaminase elevations resolved spontaneously, but Surrozen had already reported that three of the four subjects had Grade 3 ALT and AST elevations back in 2022."While no safety signal was observed at lower doses, lower-dose levels would not be expected to activate Wnt signaling and produce a pharmacologic effect in the intestine," the company noted in its statement Thursday. It also pointed to broader strategic considerations, such as significant clinical development expenses and market competition in IBD.Prioritising liver disease candidateThe company said it will instead now concentrate on another investigational treatment, SZN-043 for severe liver diseases, starting with alcohol-associated hepatitis. The compound, a hepatocyte targeted R-spondin-mimetic, is designed to stimulate the regeneration of liver cells in patients with liver disease.Results from a Phase Ia trial in patients with chronic liver disease and in healthy volunteers are due this quarter. The company expects to begin enrolling patients with alcohol-associated hepatitis in a Phase Ib study this year, and says proof-of-concept data could be available in the second half.  Surrozen is also co-developing SZN-413 with Boehringer Ingelheim as a potential treatment for retinal vascular-associated diseases. The companies joined forces on the drug in 2022 under a deal worth potentially over $586.5 million.