Trofinetide (NNZ 2566), a proprietary small molecule analogue of glycine-proline-glutamate [Glypromate®], is being developed by Neuren Pharmaceuticals and Acadia Pharmaceuticals for the treatment of brain injuries, fragile X syndrome, Rett syndrome. Trofinetide is a synthetic analogue of a naturally occurring neurotrophic peptide derived from IGF-1, a growth factor produced by brain cells. In animal models, trofinetide exhibits a wide range of important effects including inhibiting neuroinflammation, normalizing the role of microglia and correcting deficits in synaptic function. Trofinetide was approved in March 2023 in the USA for the treatment of Rett syndrome in adult and pediatric patients 2 years of age and older.

Ponesimod is an experimental drug for the treatment of multiple sclerosis (MS) graft-versus-host disease and psoriasis. It acts on certain types of white blood cells (lymphocytes) which are involved in the autoimmune attack on myelin seen in multiple sclerosis (MS). Ponesimod is an orally active, reversible, and selective sphingosine-1-phosphate receptor (S1PR1) modulator. The drug is in phase II clinical trial for the treatment of graft-versus-host disease. In addition, the phase III clinical trial comparing ponesimod to teriflunomide in relapsing-remitting MS is ongoing.

A-4250 (odevixibat) is a selective inhibitor of the ileal bile acid transporter (IBAT) that acts locally in the gut. Ileum absorbs glyco-and taurine-conjugated forms of the bile salts. IBAT is the first step in absorption at the brush-border membrane. A-4250 works by decreasing the re-absorption of bile acids from the small intestine to the liver, whichreduces the toxic levels of bile acids during the progression of the disease. It exhibits therapeutic intervention by checking the transport of bile acids. Studies show that A-4250 has the potential to decrease the damage in the liver cells and the development of fibrosis/cirrhosis of the liver known to occur in progressive familial intrahepatic cholestasis. A-4250 is a designated orphan drug in the USA for October 2012. A-4250 is a designated orphan drug in the EU for October 2016. A-4250 was awarded PRIME status for PFIC by EMA in October 2016. A-4250 is in phase II clinical trials by Albireo for the treatment of primary biliary cirrhosis (PBC) and cholestatic pruritus. In an open label Phase 2 study in children with cholestatic liver disease and pruritus, odevixibat showed reductions in serum bile acids and pruritus in most patients and exhibited a favorable overall tolerability profile.

Belzutifan (PT2977) is an orally active, small molecule inhibitor of hypoxia-inducible factor (HIF)-2alpha (HIF-2a). Upon oral administration, HIF-2alpha inhibitor PT2977 binds to and blocks the function of HIF-2alpha, thereby preventing HIF-2alpha heterodimerization and its subsequent binding to DNA. This results in decreased transcription and expression of HIF-2alpha downstream target genes, many of which regulate hypoxic signaling. This inhibits cell growth and survival of HIF-2alpha-expressing tumor cells. HIF-2alpha, the alpha subunit for the heterodimeric transcription factor HIF-2, is overexpressed in many cancers and promotes tumorigenesis.

Fosdenopterin (NulibryTM) is a synthetic cyclic pyranopterin monophosphate that is being developed by Origin Biosciences (a subsidiary of BridgeBio Pharma) for the treatment of molybdenum cofactor deficiency (MoCD) type A. Patients with MoCD Type A have mutations in the MOCS1 gene leading to deficient MOCS1A/B dependent synthesis of the intermediate substrate, cPMP. Substrate replacement therapy with NULIBRY provides an exogenous source of cPMP, which is converted to molybdopterin. Molybdopterin is then converted to molybdenum cofactor, which is needed for the activation of molybdenum-dependent enzymes, including sulfite oxidase (SOX), an enzyme that reduces levels of neurotoxic sulfites. Fosdenopterin was approved by the US FDA in February 2021 for use in reducing the risk of mortality in paediatric and adult patients with MoCD type A.

Sotorasib (LUMAKRAS™) is a RAS GTPase family inhibitor being developed by Amgen for the treatment of solid tumours with KRAS mutations, including non-small cell lung cancer (NSCLC) and colorectal cancer. Sotorasib is an inhibitor of KRASG12C, a tumor-restricted, mutant-oncogenic form of the RAS GTPase, KRAS. Sotorasib forms an irreversible, covalent bond with the unique cysteine of KRASG12C, locking the protein in an inactive state that prevents downstream signaling without affecting wild-type KRAS. Sotorasib blocked KRAS signaling, inhibited cell growth, and promoted apoptosis only in KRAS G12C tumor cell lines. Sotorasib inhibited KRASG12C in vitro and in vivo with minimal detectable off-target activity. In May 2021, sotorasib was granted accelerated approval by the US FDA for the treatment of adult patients with KRAS G12C-mutated locally advanced or metastatic NSCLC, as determined by an FDA-approved test, who have received at least one prior systemic therapy.

Voclosporin (Lupkynis™) is an oral calcineurin inhibitor immunosuppressant that is being developed by Aurinia Pharmaceuticals. Voclosporin is an analogue of cyclosporine with a modification at the amino acid-1 position. The drug has been designed to show improved potency against calcineurin inhibition and better metabolic stability than cyclosporine. Although the exact mechanism of voclosporin is not yet clear, it inhibits calcineurin, thereby blocking lymphocyte proliferation and T-cell mediated immune responses, as well as increasing podocyte integrity in the kidney. In January 2021, based on positive results from the pivotal phases II and III trials, oral voclosporin received its first approval in the USA for use in combination with a background immunosuppressive therapy regimen for adults with active lupus nephritis. Voclosporin is also being explored for the novel coronavirus disease 2019 (COVID-19) in kidney transplant recipients. Clinical evaluation of voclosporin for plaque psoriasis, coronary artery restenosis and rheumatoid arthritis has been discontinued and no recent development for prevention of renal transplant rejection has been identified since 2015.

Difelikefalin (Korsuva™) is a synthetic peptide agonist of the kappa opioid receptor being developed by Cara Therapeutics for the treatment of pruritus. In August 2021, intravenous difelikefalin was approved in the USA for the treatment of moderate-to-severe pruritus associated with chronic kidney disease (CKD) in adults undergoing haemodialysis. Difelikefalin selectively acts on kappa opioid receptors in peripheral tissues, which contribute to pruritis and nociception. The activation of opioid receptors in peripheral neurons and keratinocytes reduces afferent (sensory) impulses towards the central nervous system, decreasing pain signals. Activating kappa opioid receptors on immune cells, including monocytes and T lymphocytes, decreases the release of pro-inflammatory chemicals such as prostaglandins.

Trilaciclib (Cosela™) is a small-molecule, short-acting, inhibitor of cyclin-dependent kinases (CDK) 4 and 6 developed by G1 Therapeutics for its myeloprotection and potential antitumor efficacy and safety benefits in combination with cancer chemotherapy. CDKs govern cell cycle progression, and trilaciclib induces a transient, reversible G1 cell cycle arrest of proliferating haematopoietic stem and progenitor cells in bone marrow, thus protecting them from damage during chemotherapy. In February 2021, trilaciclib received its first approval in the USA to decrease the incidence of chemotherapy-induced myelosuppression in adult patients when administered prior to a platinum/etoposide-containing regimen or topotecan-containing regimen for extensive-stage small cell lung cancer (ES-SCLC). Clinical studies in breast cancer, colorectal cancer and small cell lung cancer are underway in several countries.

Maralixibat (Livmarli™) is a potent, apical, sodium‐dependent, bile acid transporter competitive inhibitor with minimal systemic absorption being developed by Mirum Pharmaceuticals for the treatment of rare cholestatic liver diseases including Alagille syndrome (ALGS), progressive familial intrahepatic cholestasis (PFIC) and biliary atresia. Maralixibat received its first approval on 29 September 2021, in the USA, for use in the treatment of cholestatic pruritus in patients with ALGS 1 year of age and older. Maralixibat is also under regulatory review for ALGS in Europe, and clinical development for cholestatic liver disorders including ALGS in patients under 1 year of age, PFIC and biliary atresia is continuing in several other countries. This article summarises the milestones in the development of maralixibat leading to this first approval for ALGS.