Increasingly next generation proteins are being used over traditional monoclonal antibodies. Here we explore the challenges in developing next generation protein therapeutics and the opportunities they offer. This is an extract from a whitepaper on the different approaches, competitive advantages and challenges of next gen therapeutics over traditional mAbs. Download the full whitepaper for free here.
Key challenges in developing next gen protein therapeutics
Next generation therapeutic proteins are typically generated through directed evolution. Large combinatorial libraries are created and the amino acid sequence of a patch on the scaffold surface is extensively mutated. Phage display, yeast display and/ or ribosome/mRNA display are used to isolate binding proteins. Screening, selection and storage of candidates are significant discovery hurdles to overcome that require an adequate supply to the target of interest.
One of the key challenges of next generation protein therapeutics due to their small size is rapid renal clearance. Fortunately, strategies can be developed to avoid this such as Fc fusion, binding to albumin or peptide optimisation. In addition to increasing the half life of the next generation protein therapeutic often the Fc region is fused to retain the immune effector functions of full length monoclonal antibodies for example the HAI-1-Fc fusion for targeting matriptase in cancer. Proteins may also be PEGylated in order to increase their half-life in the blood stream. The exact requirement for half-life extension varies between engineered proteins.
Novel opportunities for next gen protein therapeutics
Next generation protein therapeutics potentially provide an opportunity for protein biologics to target intracellular processes therapeutically. At present intracellular targeting is dominated by small molecules and DNA/ RNA therapeutics. Feldan Therapeutics has developed a protein-based technology platform, the Feldan Shuttle (a peptide), for direct delivery of proteins inside cells. The platform has been successfully used on several cell types including human primary cells and allowed the transfer of active nucleases, transcription factors and importantly antibodies.
Most monoclonal antibodies do not function optimally under live cell intracellular conditions. Next generation protein therapeutics can be optimised for activity intracellularly. Multivalent approaches could potentially be used to activate pathways such as apoptotic pathways in cancer cells or inhibit multiple inflammatory mediators. For example, Covagen has developed a bispecific Fynomer® antibody conjugate which targets both IL-17A and TNF. Combination with the Feldan peptide could enable novel strategies such as next generation protein therapeutics that target intracellular cancer neoantigens in order to activate immunogenic cell death pathways which would complement the field of cancer immunotherapy.
Due to their in vitro selection, next generation protein therapeutics can bind targets that convention antibodies are unable to such as G-protein coupled receptors (GPCRs) as well as ion-gated, ligand-gate and voltagegated ion channels, which provides opportunities in pain management (Knottins have been FDA approved in this indication) and immune oncology to name a couple. CXCR4 is a GPCR that regulates both cancer cells and the trafficking and homing of immune regulatory cells. Polyphor has developed a cyclic peptide inhibitor of CXCR4 called Balixafortide which has completed Phase I/ II studies in patients with metastatic HER2-negative breast cancer. Balixafortide in combination with eribulin produced a higher response rate than published data for eribulin alone in a similar patient population.
Exploiting the opportunity to create differentiated and added-value therapeutic molecules
A selection of monoclonal antibody alternatives under development will now be discussed to give a flavour of the potential of this modality. The information in this section is sourced from the respective company websites and clinicaltrials.gov. Avacta Life Sciences Limited are a discovery stage company developing Affimer® technology primarily targeting opportunities in immunooncology. Their lead candidate is an anti-PD-L1 immune checkpoint agonist for use in oncology applications that is undergoing optimisation for preclinical studies. The company is also targeting LAG-3, CD27, GITR, and CD19 (for T-cell engagement) to name a few.
Molecular Partners AG is a clinical stage company developing DARPin® Technology. The company is currently engaged in a phase I/II clinical trials of MP0250 a multi- DARPin® with three specificities, able to simultaneously neutralize the activities of vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF) and also to bind to human serum albumin (HSA) to give an increased plasma half-life and potentially enhanced tumor penetration for Multiple Myeloma, EGFR-mutated non-small cell lung cancer. The company has a phase I trial in HER2 positive cancers being targeted with MP0274, a DARPin® drug candidate targeting HER2. Abicipar is a DARPin® antagonist of Vascular Endothelial Growth Factor A (VEGF-A) that inhibits all relevant subtypes of VEGF-A with very high potency. Phase 3 clinical trials of abicipar DARPin® for wet age-related macular degeneration started in July 2015, in partnership with Allergan. Topline results are expected this year (2018).
A phase III trial is also planned for Diabetic Macular Edema. Bristol-Myers Squibb have an anti-myostatin AdnectinTM in phase I/II trial for Muscular Dystrophy taking advantage of good tissue penetration. Research Corporation Technologies has developed CH2 antibody domain nanoantibodies or ABDURINS™. A key advantage to ABDURINS™ is longer serum half-life (8-16 hrs) compared to other scaffolds of a similar molecular weight (30 min). The company is seeking partners interested in licencing the technology for drug discovery.