Single domain antibodies, or nanobodies®, are small antibody fragments from camelids (like llamas) with unique binding flexibility, allowing them to access normally difficult to reach epitopes and target challenging antigens. Their small size, high stability, and lower production costs make them advantageous over conventional antibodies for diagnostics and targeted therapies.
At Mithridate we use (AI-optimized) single domain antibodies to design and engineer therapeutic proteins tailored to our needs.
Currently our pipeline consists of three highly innovative constructs that are in pre-clinical development for a variety of purposes:
Anticoagulants (or blood thinners) are used for the prevention of thrombosis. For instance, to prevent stroke in patients with atrial fibrillation or to prevent venous thromboembolism (deep venous thrombosis or pulmonary embolism). Different classes of anticoagulants are available, but the class of factor Xa inhibitors (apixaban, rivaroxaban and edoxaban) is gaining ground. Antithrombotic therapy is associated with a risk for bleeding, which can be life-threatening.
Worldwide, approximately 25 million people are prescribed factor Xa inhibitors and on annual basis, approximately 2-3% of these patients experience severe bleeding, leading to high incidence of disability and mortality especially in anticoagulant related stroke. This emphasizes the high medical need to reverse the action of FXa inhibitors in acute situations. Current products like PCC (off label) and andexanet carry a risk of thrombosis and have several other disadvantages.
Mithridate has engineered both selective and universal factor Xa reversal single domain antibody constructs to reverse the action of any factor Xa inhibitor. In some cases, artificial intelligence was used to optimize binding affinity.
Since these single domain antibodies, unlike other solutions, target the anticoagulant itself and leave the clotting system untouched, less side effects (like thrombosis) are anticipated. In addition, the product will be developed as a ready to use solution for injection or infusion, which facilitates fast and easy administration. In addition, single domain antibodies are much easier (and thus cheaper) to produce than other recombinant proteins.
TTP, is a rare, chronic and potentially life-threatening blood disease that causes blood clots and bleedings at the same time. Due to microthrombi (small blood clots) in the smaller vessels of vital organs such as the brain, kidneys and heart, tissue ischemia may occur and lead to organ failure. Concomitant thrombocytopenia (depletion of platelets) increases the risk of bleeding, which on the skin is visible as purpura (bruises). The consequences of microthrombi can be severe, potentially resulting in acute thromboembolic events such as stroke and myocardial infarction.
The disease is caused by severe inhibition and/or depletion of the enzyme ADAMTS13, which cleaves von Willebrand Factor (VWF), a protein that plays an important role in blood clotting. In TTP patients, VWF is not cleaved properly, leading to the accumulation of ultra-large VWF multimers that promote adhesion of platelets to VWF strands and microthrombi formation, resulting in reduced platelet numbers and an increased risk of bleedings.
The vast majority (95%) of TTP cases is acquired and caused by auto-antibodies directed against a specific region of ADAMTS13. This autoimmune form is called acquired or immune-mediated TTP (aTTP or iTTP). The remaining 5% of cases are congenital (cTTP), caused by inherited genetic mutations in ADAMTS13.
Current treatment comprises therapeutic plasma exchange (TPE, a few days for several hours) to remove auto-antibodies and replenish ADAMTS13, immunosuppressive therapy to reduce autoantibody formation, and caplacizumab; a single domain antibody directed against VWF that prevents platelet binding to VWF. Although treatment (especially TPE and immune suppression) reduced mortality from 90% to ±5%, there is still a high medical need to reduce disease burden and mortality.
Mithridate has engineered an innovative therapeutic protein (MIT-2002) that consists of a truncated ADAMTS13 enzyme that is less sensitive to autoantibodies and is fused with a selective anti-VWF single domain antibody. As such, MIT-2002 has a clear dual action to prevent thrombus formation: it restores ADAMTS13 function even in the presence of autoantibodies and prevents platelet binding to VWF.
The fibrinolytic system is responsible for breaking down blood clots and plays a central role in maintaining hemostatic balance. It functions primarily through the conversion of inactive plasminogen into active plasmin, an enzyme that degrades the fibrin meshwork of blood clots. This process is crucial for preventing excessive clotting (thrombosis) and for enabling wound healing by clearing fibrin deposits and extracellular matrix.
Plasminogen is activated by tissue plasminogen activator (tPA) and urokinase (uPA). tPA-mediated conversion of plasminogen into plasmin requires binding to fibrin, while uPA activates plasminogen independent of fibrin.
Plasminogen activators (fibrinolytics) are used to treat thromboembolic diseases. Currently, the most effective clinical agent for this purpose is recombinant tPA. The efficacy of rtPA is primarily due to its fibrin-binding domain and its catalytic domain that activates plasminogen. Despite its effectiveness, rtPA has several limitations. rtPA is relatively unstable when dissolved in physiological buffers, complicating treatment logistics. Additionally, the production of tPA is challenging due to its complexity, and manufacturing issues can lead to reduced availability of this crucial therapeutic agent. As such, there is a need for a fibrinolytic agent that is more stable, easier to produce, and as effective, if not more so, than rtPA.
Another limitation of plasminogen activators like rtPA is their non-specific proteins like fibrinogen which can lead to systemic effects, such as unwanted tissue degradation or excessive bleeding. One potential strategy to improve specificity is to link plasminogen activator to a targeting antibody. However, many commonly used antibodies cross-react with fibrinogen, limiting their suitability for this purpose.
At Mithridate we have engineered a novel fibrinolytic by coupling uPA, which is smaller, easier to produce and more active than tPA, to a fibrin specific single domain antibody. This fusion protein has a high production efficiency, is stable in solution and is at least equi-effective as rtPA.
