Hepcidin Therapeutics
Greg Anderson Iron Metabolism Laboratory QIMR Berghofer Medical Research Institute Disclosure
- Consultant for Protagonist Therapeutics - No financial interest in the company Iron intake and excretion
Diet
Intestinal uptake X Regulation of iron homeostasis
Liver Hepcidin
Macrophages Small intestine
Fe
Iron Plasma Utilization Transferrin Hepcidin – master regulator of iron homeostasis
Produced by the liver in response to variations in iron requirements. Regulates iron release from various body cells.
Enterocyte Macrophage
Fpn1 Fpn1
Hepcidin Hepcidin – master regulator of iron homeostasis
Produced by the liver in response to variations in iron requirements. Regulates iron release from various body cells.
Enterocyte Macrophage
Fpn1 Fpn1
By affecting several tissues at once hepcidin allows the coordinated release of iron from multiple sites. Hepcidin and iron absorption
Low hepcidin means high iron absorption
High hepcidin means low iron absorption
Under normal conditions hepcidin increases as body iron levels increase, limiting further iron intake.
In haemochromatosis, hepcidin remains relatively low despite increased body iron levels.
Thus iron absorption is inappropriately high. HFE controls hepcidin expression
Bridle et al. 2003 Lancet 361:669-673 Regulation of iron homeostasis
HypoxiaIron stores/erythropoiesis Inflammation
Iron Erythropoiesis Stores Hepcidin
DMT1 FPN FPN Fe2+
Fe3+ Hp Cp
Fe2Tf Strategies for treating iron overload
Reduce current iron load Venesection Iron chelation
Prevent further iron accumulation
Reducing the amount of iron in the diet Agents that bind iron in the diet and render it non-absorbable Using drugs to block iron absorption by the intestine Increasing hepcidin levels to reduce iron absorption
Both issues need to be addressed Strategies for reducing iron loading
Reduce current iron load Venesection Iron chelation
Prevent further iron accumulation
Reducing the amount of iron in the diet Agents that bind iron in the diet and render it non-absorbable Using drugs to block iron absorption by the intestine Increasing hepcidin levels to reduce iron absorption
Both issues need to be addressed Hepcidin related therapeutic agents
The problem in HH: There is not enough hepcidin.
Potential solutions:
Administer hepcidin itself Administer agents that act like hepcidin (functional analogs) Increase hepcidin production by stimulating its regulatory pathway
Delivery is important. Hepcidin is produced internally Exogenous administration needs to be convenient Periodic oral administration is ideal Hepcidin related therapeutic agents
Synthetic BMP6 hepcidin
Minihepcidins TMPRSS6 antagonists
Other hepcidin peptides Full-length hepcidin
Just giving hepcidin would be the obvious thing to do.
But it is not so simple: 25 amino acids long 4 disulfide bonds (105 different folds possible) Production of correctly folded peptide expensive Folding yield only 6-12% Short half life
So not an ideal option Candidate hepcidin therapeutics
Agent Type Administration Animal Human trials studies Hepcidin replacement Various Peptide i.p.; oral Yes No LJPC-401 Peptide s.c. Yes Yes M012 Peptide ? Yes Yes PTG300 Peptide s.c. Yes Yes Stimulation of hepcidin expression Progesterone Small molecule i.p Yes No
BMP6 Protein i.p. Yes No TMPSS6 antisense Antisense s.c. Yes No oligonucleotide oligonucleotide LNP-RNAi siRNA i.v.; s.c. Yes No Minihepcidin
Mouse – iron deficient wild-type and Hamp KO Intraperitoneal, oral.
Preza et al. 2011. J Clin Invest 121: 4880-4888 Minihepcidin
Mouse - Hamp KO Subcutaneous
Ramos et al. 2012. Blood 120: 3829-3836 BMP6
Mouse - Hfe KO - intraperitoneal.
Corradini et al. 2010. Gastroenterology 139: 1721-1729 TMPRSS6 antagonist (LNP-siRNA)
Mouse – Hbbth3/+(thalassaemia) Intravenous
Schmidt et al. 2015. Am J Hematol 90: 310-313 Hepcidin mimetics – Pre-clinical and Phase I
La Jolla Pharmaceuticals – LJPC-401 (lead candidate) = formulation of Hepcidin • INSERM licensed PR73 • Aggregation and solubility issues • Phase 1 initiated 2016 Q1
Merganser Biotech – Lead Candidate M012 Mini-hepcidin • Assumed close analog of PR73 where free sulfhydryl is protected as a hetero-disulfide (-SMe protected) • Free sulfhydryl group has the liabilities of instability and intermediate(s) that promote protein aggregation, precipitation and toxicity issues
Protagonist Therapeutics – Lead Candidate PTG300 – Currently undergoing IND enabling studies expect Phase I early 2017 Merganser Biotech Minihepcidin M012 ecdnisanimportanttherapeutic target Hepcidin Antagonists Agonists BMP6 analogs ecdnagonists Hepcidin TMPRSS6 antagonists ferroportin bindingto hepcidin Inhibitors of synthesis Inhibitors of hepcidin TfR2 or or traps BMP6 antagonists traps Hepcidin Class Antibodies, smallmolecules siRNAs, antisense oligonucleotides synthesis Inhibitors of hepcidin TfR2 or Heparin derivatives, BMP receptor scaffolds, Antibodies, lipocalin siRNAs, antisenseoligonucleotides Proteins 7-9 aminoacidpeptides Compounds hemojuvelin kinase inhibitors, soluble spiegelmers az2013. Ganz hso Rev 93 Physiol :1721-1741 What comes next?
Further clinical trials: - Phase I - Phase II - Phase III - Phase IV
These take time (and money!!!)
A large pharmaceutical company will need involvement
If all goes well, it may still be 5 years before a product is available for routine use Other things to think about
New oral iron chelators
Other hepcidin-related approaches
Blocking iron absorption, e.g. DMT1 inhibitors
Will this become a thing of the past?