Gene therapy | |
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Target gene | LPL |
Vector | Adeno-associated virus 1 |
Clinical data | |
Trade names | Glybera |
AHFS/Drugs.com | UK Drug Information |
License data | |
Routes of administration | Intramuscular injection |
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Alipogene tiparvovec, sold under the brand name Glybera, is a gene therapy treatment designed to reverse lipoprotein lipase deficiency (LPLD), a rare recessive disorder, due to mutations in LPL, which can cause severe pancreatitis. [1] It was recommended for approval by the European Medicines Agency in July 2012 and approved by the European Commission in November of the same year. It was the first marketing authorisation for a gene therapy treatment in either Europe or the United States. [2] [3]
The drug is administered via a series of injections into the leg muscles – as many as 60, all in one session. [4] It is a one-time treatment intended to last at least ten years.
Glybera gained infamy as the "million-dollar drug" and proved commercially unsuccessful for a number of reasons. [4] [5] Its cost to patients and payers, together with the rarity of LPLD, high maintenance costs to its manufacturer uniQure, and failure to achieve approval in the US, led to uniQure withdrawing the drug after two years on the EU market. As of 2018, only 31 people worldwide have ever been administered Glybera, and uniQure has no plans to sell the drug in the US or Canada. [4] [5]
Glybera was developed over a period of decades by researchers at the University of British Columbia (UBC). [4] In 1986, Michael R. Hayden and John Kastelein began research at UBC, confirming the hypothesis that LPLD was caused by a gene mutation. Years later, in 2002, Hayden and Colin Ross successfully performed gene therapy on test mice to treat LPLD; their findings were featured on the September 2004 cover of Human Gene Therapy . Ross and Hayden next succeeded in treating cats in the same manner, with the help of Boyce Jones. [4]
Meanwhile, Kastelein—who had, by 1998, become an international expert in lipid disorders—co-founded Amsterdam Molecular Therapeutics (AMT), which acquired rights to Hayden's research with the aim of releasing the drug in Europe.
Since LPLD is a rare condition (prevalence worldwide 1–2 per million), related clinical tests and trials have involved unusually small cohort sizes. The first main trial (CT-AMT-011-01) involved just 14 subjects, [6] and by 2015, a total of 27 individuals had been involved in phase III testing. [7] The second phase of testing focused on subjects living along the Saguenay River in Quebec, where LPLD affects people at the highest rate in the world (up to 200 per million) due to the founder effect.
After over two years of testing, Glybera was approved in the European Union in 2012. [8] However, after spending millions of euros on Glybera's approval, AMT went bankrupt and its assets were acquired by uniQure. [4]
Alipogene tiparvovec was expected to cost around $1.6 million per treatment in 2012 [9] —revised to $1 million in 2015 [10] —making it the most expensive medicine in the world at the time. [11] However, replacement therapy, a similar treatment, can cost over $300,000 per year, for life. [4]
In 2015, uniQure dropped its plans for approval in the US and exclusively licensed rights to sell the drug in Europe to Chiesi Farmaceutici for €31 million. [8] [4]
As of 2016, only one person had received the drug outside of a clinical trial. [8]
In April 2017, Chiesi quit selling Glybera and uniQure announced that it would not pursue the renewal of the marketing authorisation in the European Union when it was scheduled to expire that October, due to lack of demand. [12] Afterwards, the three remaining doses in Chiesi's inventory were administered to three patients for €1 each. [4]
The adeno-associated virus serotype 1 (AAV1) viral vector delivers an intact copy of the human lipoprotein lipase (LPL) gene to muscle cells. The LPL gene is not inserted into the cell's chromosomes but remains as free floating DNA in the nucleus. The injection is followed by immunosuppressive therapy to prevent immune reactions to the virus. [3]
Data from the clinical trials indicates that fat concentrations in blood were reduced between 3 and 12 weeks after injection, in nearly all patients. The advantages of AAV include apparent lack of pathogenicity, delivery to non-dividing cells, and much smaller risk of insertion [13] compared to retroviruses, which show random insertion with accompanying risk of cancer. AAV also presents very low immunogenicity, mainly restricted to generating neutralising antibodies, and little well defined cytotoxic response. [14] [15] [16] The cloning capacity of the vector is limited to replacement of the virus's 4.8 kilobase genome.
Gene therapy is a medical technology which aims to produce a therapeutic effect through the manipulation of gene expression or through altering the biological properties of living cells.
Human genetic enhancement or human genetic engineering refers to human enhancement by means of a genetic modification. This could be done in order to cure diseases, prevent the possibility of getting a particular disease, to improve athlete performance in sporting events, or to change physical appearance, metabolism, and even improve physical capabilities and mental faculties such as memory and intelligence. These genetic enhancements may or may not be done in such a way that the change is heritable.
Lipoprotein lipase (LPL) (EC 3.1.1.34, systematic name triacylglycerol acylhydrolase (lipoprotein-dependent)) is a member of the lipase gene family, which includes pancreatic lipase, hepatic lipase, and endothelial lipase. It is a water-soluble enzyme that hydrolyzes triglycerides in lipoproteins, such as those found in chylomicrons and very low-density lipoproteins (VLDL), into two free fatty acids and one monoacylglycerol molecule:
Virotherapy is a treatment using biotechnology to convert viruses into therapeutic agents by reprogramming viruses to treat diseases. There are three main branches of virotherapy: anti-cancer oncolytic viruses, viral vectors for gene therapy and viral immunotherapy. These branches use three different types of treatment methods: gene overexpression, gene knockout, and suicide gene delivery. Gene overexpression adds genetic sequences that compensate for low to zero levels of needed gene expression. Gene knockout uses RNA methods to silence or reduce expression of disease-causing genes. Suicide gene delivery introduces genetic sequences that induce an apoptotic response in cells, usually to kill cancerous growths. In a slightly different context, virotherapy can also refer more broadly to the use of viruses to treat certain medical conditions by killing pathogens.
Adeno-associated viruses (AAV) are small viruses that infect humans and some other primate species. They belong to the genus Dependoparvovirus, which in turn belongs to the family Parvoviridae. They are small replication-defective, nonenveloped viruses and have linear single-stranded DNA (ssDNA) genome of approximately 4.8 kilobases (kb).
A helper dependent virus, also termed a gutless virus, is a synthetic viral vector dependent on the assistance of a helper virus in order to replicate, and can be used for purposes such as gene therapy. Naturally-occurring satellite viruses are also helper virus dependent, and can sometimes be modified to become viral vectors.
Familial hypercholesterolemia (FH) is a genetic disorder characterized by high cholesterol levels, specifically very high levels of low-density lipoprotein cholesterol, in the blood and early cardiovascular diseases. The most common mutations diminish the number of functional LDL receptors in the liver or produce abnormal LDL receptors that never go to the cell surface to function properly. Since the underlying body biochemistry is slightly different in individuals with FH, their high cholesterol levels are less responsive to the kinds of cholesterol control methods which are usually more effective in people without FH. Nevertheless, treatment is usually effective.
Lipoprotein lipase deficiency is a genetic disorder in which a person has a defective gene for lipoprotein lipase, which leads to very high triglycerides, which in turn causes stomach pain and deposits of fat under the skin, and which can lead to problems with the pancreas and liver, which in turn can lead to diabetes. The disorder only occurs if a child acquires the defective gene from both parents. It is managed by restricting fat in diet to less than 20 g/day.
In biochemistry, lipase refers to a class of enzymes that catalyzes the hydrolysis of fats. Some lipases display broad substrate scope including esters of cholesterol, phospholipids, and of lipid-soluble vitamins and sphingomyelinases; however, these are usually treated separately from "conventional" lipases. Unlike esterases, which function in water, lipases "are activated only when adsorbed to an oil–water interface". Lipases perform essential roles in digestion, transport and processing of dietary lipids in most, if not all, organisms.
Gene therapy using lentiviral vectors was being explored in early stage trials as of 2009.
Familial hypertriglyceridemia is a genetic disorder characterized by the liver overproducing very-low-density lipoproteins (VLDL). As a result, an affected individual will have an excessive number of VLDL and triglycerides on a lipid profile. This genetic disorder usually follows an autosomal dominant inheritance pattern. The disorder presents clinically in patients with mild to moderate elevations in triglyceride levels. Familial hypertriglyceridemia is typically associated with other co-morbid conditions such as hypertension, obesity, and hyperglycemia. Individuals with the disorder are mostly heterozygous in an inactivating mutation of the gene encoding for lipoprotein lipase (LPL). This sole mutation can markedly elevate serum triglyceride levels. However, when combined with other medications or pathologies it can further elevate serum triglyceride levels to pathologic levels. Substantial increases in serum triglyceride levels can lead to certain clinical signs and the development of acute pancreatitis.
Lysosomal acid lipase deficiency is an autosomal recessive inborn error of metabolism that results in the body not producing enough active lysosomal acid lipase (LAL) enzyme. This enzyme plays an important role in breaking down fatty material in the body. Infants, children and adults that have LAL deficiency experience a range of serious health problems. The lack of the LAL enzyme can lead to a build-up of fatty material in a number of body organs including the liver, spleen, gut, in the wall of blood vessels and other important organs.
Self-complementary adeno-associated virus (scAAV) is a viral vector engineered from the naturally occurring adeno-associated virus (AAV) to be used as a tool for gene therapy. Use of recombinant AAV (rAAV) has been successful in clinical trials addressing a variety of diseases. This lab-made progeny of rAAV is termed "self-complementary" because the coding region has been designed to form an intra-molecular double-stranded DNA template. A rate-limiting step for the standard AAV genome involves the second-strand synthesis since the typical AAV genome is a single-stranded DNA template. However, this is not the case for scAAV genomes. Upon infection, rather than waiting for cell mediated synthesis of the second strand, the two complementary halves of scAAV will associate to form one double stranded DNA (dsDNA) unit that is ready for immediate replication and transcription. The caveat of this construct is that instead of the full coding capacity found in rAAV (4.7–6kb) scAAV can only hold about half of that amount (≈2.4kb).
Adeno-associated virus (AAV) has been researched as a viral vector in gene therapy for cancer treatment as an Oncolytic Virus. Currently there are not any FDA approved AAV cancer treatments, as the first FDA approved AAV treatment was approved December 2017. However, there are many Oncolytic AAV applications that are in development and have been researched.
Richard Jude Samulski is an American scientist, inventor, and academic recognized for his pioneering work in gene therapy and adeno-associated virus vectors (AAV) in the fields of molecular virology and pharmacology.
Jean Bennett is the F. M. Kirby Professor of Ophthalmology in the Perelman School of Medicine at the University of Pennsylvania. Her research focuses on gene therapy for retinal diseases. Her laboratory developed the first FDA approved gene therapy for use in humans, which treats a rare form of blindness. She was elected a member of the National Academy of Sciences in 2022.
Mavis Agbandje-McKenna was a Nigerian-born British medical biophysicist, structural virologist, and a professor of structural biology, as well as the director of the Center for Structural Biology at the University of Florida in Gainesville, Florida. Agbandje-McKenna studied parvovirus structures using X-ray crystallography and cryogenic electron microscopy and did much of the initial work to elucidate the basic structure and function of adeno-associated viruses (AAVs). Her viral characterization and elucidation of antibody binding sites on AAV capsids has led to the development of viral capsid development and gene therapy approaches that evade immune detection and can be used to treat human diseases such as muscular dystrophies. Agbandje-McKenna was recognized with the 2020 American Society of Gene and Cell Therapy Outstanding Achievement Award for her contributions to the field. She died in 2021 from amyotrophic lateral sclerosis.
Valoctocogene roxaparvovec, sold under the brand name Roctavian, is a gene therapy used for the treatment of hemophilia A. It was developed by BioMarin Pharmaceutical. Valoctocogene roxaparvovec is made of a virus (AAV5) that has been modified to contain the gene for factor VIII, which is lacking in people with hemophilia A. It is an adeno-associated virus vector-based gene therapy. It is given by intravenous infusion.
Etranacogene dezaparvovec, sold under the brand name Hemgenix is a gene therapy used for the treatment of hemophilia B. Etranacogene dezaparvovec is an adeno-associated virus vector-based gene therapy which consists of a viral vector carrying a gene for clotting Factor IX. The gene is expressed in the liver to produce Factor IX protein, to increase blood levels of Factor IX and thereby limit bleeding episodes. Hemophilia B is a genetic bleeding disorder resulting from missing or insufficient levels of blood clotting Factor IX, a protein needed to produce blood clots to stop bleeding.