Alipogene tiparvovec

Alipogene tiparvovec contains the human lipoprotein lipase (LPL) gene variant LPLS447X in a vector. The human LPL gene variant LPL^S447X in an adeno-associated virus serotype 1 (AAV1) vector intended to target the muscle. Alipogene tiparvovec is injected as a one-time series into the muscle of the lower extremities where it is taken up by myocytes. The elements of the vector were chosen such that expression of the LPL^S447X gene is promoted, by co-opting the expression machinery of the cell and the myocytes produce the protein product of the transgene LPL^S447X without the vector being able to reproduce itself.

Lipoprotein lipase is a key ‘first step’ enzyme in the metabolism of lipoproteins following fat intake with diet. In clinical studies a transient reduction in triglycerides for up to 12 weeks in individual patients could be observed. Furthermore, alipogene tiparvovec allows expression of the LPL protein in injected muscle which is reflected by the improvement of postprandial chylomicron (CM) metabolism observed in a small subset of patients.

Alipogene tiparvovec is expected to be degraded by endogenous protein and DNA catabolic pathways.

Non-clinical biodistribution

Following intramuscular administration of alipogene tiparvovec to mice, vector DNA was transiently detected in the circulation. Eight days after administration, high levels of vector DNA sequence were detected in injected muscle and the draining lymph nodes. Except for the site of injection, the highest vector DNA copy numbers were found in the liver and blood. The lowest number of copies was found in the brain, lung, heart and non-injected groups of muscle. In gonads and reproductive organs, vector DNA copies were found at low levels. After time, residual vector DNA levels remained high in the injected muscle and inguinal lymph nodes while decreasing steadily in the other organs. The levels of alipogene tiparvovec vector DNA found in gonads were measurable but lower than in other non-target organs.

Immunosuppressant co-treatment did not influence the biodistribution pattern neither at low dose nor at high dose in mice. The biodistribution pattern was very similar in the other tested species (cats and rabbits).

Clinical pharmacokinetics and shedding

Shedding was assessed in the clinical studies by collecting saliva, urine and semen. In CT-AMT-011-02 faeces was also collected. After administration of alipogene tiparvovec to the participants, the highest vector DNA concentrations were detected in the serum, with clearance by one to two logs per week.

In saliva vector DNA was still detectable up to 12 weeks; in urine up to 10 weeks and in semen up to 26 weeks. All but two patients received immunosuppressant for 12 weeks. There is the theoretical risk that the co-administration of the immunosuppressant regime leads to longer persistence of virus DNA in serum and as well to longer shedding in saliva, urine and semen.

High levels of vector DNA were observed up to 12 months after dosing in the target tissue for alipogene tiparvovec, injected leg muscle, but not in non-injected muscle.

Pharmacokinetics in special populations e.g. elderly/renal impairment etc.

Alipogene tiparvovec is injected directly into the target organ, skeletal muscle. Liver and kidney function, cytochrome P450 polymorphisms and ageing are not expected to influence the clinical efficacy or safety of alipogene tiparvovec.

Upon injection, alipogene tiparvovec was well tolerated in all animal studies performed with no notable clinical signs. In mice local cellular infiltrates and signs of degeneration and regeneration without necrosis, were seen at the clinical dose in the injected muscle upon histopathological examination. These effects were dose-dependent but showed regression with time. As expected, all animals developed antibodies to the AAV protein shell.

Upon treatment four weeks prior to mating, no maternal, foetal and developmental toxicity was seen in mice. No vector DNA could be detected in the foetuses after treatment of either the females or the males prior to mating.

Carcinogenicity studies have not been conducted. However in toxicity studies, no increase in tumour was identified. Although there is no fully adequate animal model to address the tumourigenic potential, the available toxicological data do not suggest any concern for tumourigenicity.