Trove Technology Platform
Secretoglobins (SCGBs) are naturally occurring proteins produced in the body by various organs. The SCGBs produced in the lungs are some of the most abundant proteins secreted in the airways. Trove and its partners have identified several SCGB candidates as potential therapeutics, with the lead candidate being recombinant human SCGB1A1 protein called Therabron™. In healthy individuals, Club cells are abundant in the airway epithelium and they produce the SCGB1A1 protein, which is the most abundant protein in the fluid that lines the respiratory tract, including the lungs and nasal airways. SCGB1A1 modulates inflammatory and immune responses to environmental irritants, pathogens, pollutants, and allergens on airway surfaces, maintains airway epithelial homeostasis, pulmonary immune homeostasis, and pulmonary vascular homeostasis via several mechanisms of action, and facilitates repair of injured or damaged airways. The SCGB1A1 protein has been studied extensively and is also known as CC10, CCSP, CC16, uteroglobin, urine protein 1, UP-1, blastokinin, and PCB-binding protein.
Respiratory tract damage and lung impairment can be caused by numerous insults, including infectious pathogens, allergens, dust or smoke, chemicals, noxious gases, inert particles, and many other potential irritants. When lungs are exposed to these insults, an inflammatory response is triggered, which often causes more physical damage to the lungs, leading to acute lung injury, loss of lung function, and/or long term fibrosis. SCGB1A1 has been shown to be critical in mitigating lung injuries and accelerating airway epithelial repair. In fact, effective lung repair is dependent upon Club cell function and a process called autophagy, which, in turn, requires sufficient SCGB1A1.
SCGB1A1 deficiency: Many patients with acute and chronic respiratory conditions are not able to produce sufficient SCGB1A1 due to a lack of sufficient Club cells. In recurrent and chronic sinusitis, the nasal airway cells that produce SCGB1A1 are replaced by fibrotic cells and scar tissue, resulting in a deficiency of SCGB1A1 which pre-disposes patients towards persistent infections and further scarring, often eventually requiring sinus surgery. There are also well-characterized deficiencies of Club cells and SCGB1A1 in the lungs in several chronic respiratory diseases (CLDs) and conditions, including COPD, asthma, CLAD-BOS, cystic fibrosis, and nasal allergy. Similarly, in Acute Lung Injury (ALI), acute respiratory distress syndrome (ARDS), and pneumonia due to influenza-like illness (flu, COVID-19, RSV), smoke inhalation, and other causes, the normal lung epithelial cells are damaged, resulting in loss of Club cells, SCGB1A1 production, and compromised lung function.
Recombinant human SCGB1A1 protein, called Therabron™, is being developed as a therapeutic to treat these respiratory conditions. Therabron™ is a replacement therapy for the missing SCGB1A1 protein and can reduce the severe inflammation, fibrosis, and loss of lung function brought about by disease and injury through its multi-modal effects. The administration of Therabron™ in models of acute and chronic respiratory conditions reduced viral load, reduced pulmonary and systemic inflammation, protected and preserved mechanical lung function and gas exchange, reduced pulmonary edema, reduced pulmonary fibrosis, and stimulated airway repair. Therabron’s stimulation of airway repair may facilitate respiratory rehabilitation following hospital discharge, severe infection, and/or inhalation injuries caused by exposures to wildfire smoke, burn pits, occupational exposures, and other airborne inhalation hazards.
Therabron™ Activities and Mechanisms of Action
SCGB1A1 and Therabron™ are multi-modal proteins engineered by nature to regulate inflammatory, fibrotic, and immune processes through multiple mechanisms of action. At least eight distinct biological activities and pathways are strongly affected by SCGB1A1 and Therabron™:
1) PLA2s: SCGB1A1 and Therabron™ inhibit at least 3 PLA2 enzymes, including sPLA2-Type 1b, sPLA2-Type 2a, and cPLA2-Type IV. Phospholipase A2s (PLA2) are enzymes found in many tissues and catalyze the hydrolysis of glycerophospholipids to release arachidonic acid (AA), particularly cPLA2-Type IV. AA is a substrate for a variety of other enzymes in the AA cascade that leads to the formation of eicosanoid mediators of inflammation, such as leukotrienes, which are associated with the severity and progression of chronic lung diseases in adults, including COPD and asthma. The activity of sPLA2-Type 1b and Type 2a are elevated during inflammatory responses, resulting in accelerated degradation of lung surfactant that can cause or exacerbate respiratory failure.
2) Influx of Innate Immune Cells and Release of Inflammatory Cytokines: The influx of neutrophils and monocytes into the lungs of individuals with Acute Lung Injury (ALI) or ARDS contributes to life-threatening inflammation, loss of lung function, and respiratory failure. In chronic lung diseases (CLDs) such as COPD, CLAD-BOS, or asthma are also characterized by an influx of neutrophils, monocytes, and/or eosinophils, which is also suppressed by SCGB1A1 and Therabron™. These influxes are strongly inhibited by Therabron™. Likewise, pro-inflammatory cytokines released in ALI and CLDs attract innate immune cells, and further enhance inflammation and tissue damage. These cytokines include IL-4, IL-5, IL-6, IL-8, IL-13, TNF-α, IL-1β, etc.; all of which are strongly reduced by Therabron™.
3) NF-KB and MAPK: Nuclear factor kappa B and p38-MAPK are master molecular switches that can turn on multiple inflammatory pathways in the lung and in many other tissues in response to inflammatory stimuli and lung injury. NF-KB normally maintains a low level of activity, but when a cell experiences an insult or receives a pro-inflammatory signal from another cell, NF-KB is activated, translocates into the cell nucleus, and increases the transcription of pro-inflammatory mediators. Native SCGB1A1 and Therabron™ suppress the activation of NF-KB, both in vitro and in vivo and thereby suppresses inflammation and the fibrosis caused by triggering of the NF-KB signal transduction pathway. Likewise, SCGB1A1 and Therabron™ inhibit phosphorylation of p38-MAPK in airway epithelial cells, simultaneously with inhibition of NF-KB p65 phosphorylation, resulting in reduction of pulmonary inflammatory and fibrotic phenotypes in multiple types of injuries in vivo.
4) Vascular permeability: Another aspect associated with severe inflammation, ALI, ARDS, severe smoke inhalation, and sepsis is increased vascular permeability, which results in pulmonary edema and/or shock. Pneumonia is characterized by severe pulmonary edema (fluid in the lungs). Pneumonia and shock are life-threatening conditions with limited treatment options at this time. Therabron™ has demonstrated that it suppresses fluid accumulation, pulmonary edema, and shock due to ALI in vivo. The molecular mechanisms of Therabron’s anti-edema effects are under investigation.
5) Transglutaminases: Transglutaminases are enzymes that cross-link proteins to other proteins by forming glutamine to lysine linkages in the presence of calcium and by forming or rearranging disulfide bonds between cysteine residues in the absence of calcium. SCGB1A1 and Therabron™ are substrates for transglutaminase 2 (“TG-2”, also known as tissue transglutaminase) and Factor XIIIa, a coagulation factor that plays a role in strengthening blood clots. TG-2 can cross-link Therabron™ to fibronectin in vitro. TG-2 plays a role in cell cycle regulation and apoptosis, cellular transport processes, formation of the extracellular matrix (ECM), cell adhesion to the ECM, cell-cell interactions, immune cell migration and maturation, and other numerous processes.
6) Fibronectin binding: SCGB1A1 and Therabron™ bind to fibronectin (Fn) in vitro and in vivo to block Fn deposition, to block Fn-Fn oligomerization and formation of fibrils required for the genesis of fibrosis, to block cellular adhesion to the ECM and migration through the ECM (including fibroblasts and white cells), and to inhibit the proliferation of fibroblasts. In short, Fn binding is a major mechanism by which SCGB1A1 and Therabron™ inhibit fibrosis.
7) Immune modulation: Deficiency of native SCGB1A1 is associated with more severe inflammatory, fibrotic, and immunologic responses to inhaled allergens, pathogens, pollutants, and particulates such as cigarette smoke. Clinically, SCGB1A1 deficiency in humans is associated with more severe asthma, allergy, COPD, and predisposition towards respiratory infection, as well as certain autoimmune diseases and increased predisposition towards transplant rejection. Administration of Therabron™ reduces these inflammatory, fibrotic, and immunologic responses in various disease models, including reducing innate immune responses, antigen-specific TH1, TH2, and TH17 responses (T-cells and B-cells). In one in vitro study, Therabron™ affected antigen uptake, processing, and/or presentation by monocyte-derived dendritic cells to reduce recognition of antigen by downstream TH2 cells. Receptors for SCGB1A1 have been identified on white cells that play a role in these processes and are under investigation by Trove and its collaborators. There are numerous applications for Therabron™ and its derivatives in immune modulation and immune tolerance applications.
8) ROS modification and potency enhancement: SCGB1A1 and Therabron™ detoxify the local environment by absorbing reactive oxygen species (ROS), which are strong oxidants that are generated during severe inflammation and that damage cells and tissues. Native SCGB1A1 is chemically modified by ROS in vivo and Trove and its partners recently discovered that similar modifications by ROS can be made to Therabron™ in vitro. Typically, ROS-mediated modifications result in loss of function and protein degradation, but our research has found that certain reaction products created by exposing Therabron™ to ROS in vitro result in a gain of function in several potency assays. For example, in NF-κB and MAPK activation assays in airway epithelial cells, Therabron’s potency is enhanced by at least 100-fold by ROS modification. Trove and its collaborators are screening libraries of chemically modified Therabron™ for anti-inflammatory and other activities to identify new, more potent isoforms of recombinant human SCGB1A1, and the receptors and mechanisms through which they operate, that may someday be used to generate second generation SCGB1A1-based therapeutics.