Teplizumab

Mechanism of action

Teplizumab binds to CD3 (a cell surface antigen present on T lymphocytes) and delays disease progression in patients with stage 2 T1D. The mechanism may involve partial agonistic signalling leading to deactivation of autoreactive CD8+ T lymphocytes and reduced immune-mediated beta-cell destruction. Teplizumab leads to an increase in the proportion of CD8+ T cells with signs of exhaustion in peripheral blood.

Pharmacodynamic properties

Clinical studies have shown that teplizumab binds to CD3 molecules on the surface of both CD4+ and CD8+ T cells during treatment, with internalisation of the teplizumab/CD3 complex from the surface of T cells. Pharmacodynamic effects include transient lymphopenia with a reduction in circulating T cells with a nadir on the 5th day of dosing, during a 14-day course of teplizumab treatment. Teplizumab exposure-response relationship and time course of pharmacodynamic response for the safety and effectiveness of teplizumab have not been fully characterised.

Pharmacokinetic properties

Steady state concentrations of teplizumab are not expected to be achieved during the 14-day course of teplizumab.

Absorption

There is no information about absorption since teplizumab is administered intravenously.

Distribution

No protein binding studies were conducted as teplizumab is a monoclonal antibody.

Metabolism

Teplizumab is expected to be metabolised into small peptides by catabolic pathways.

Elimination

The apparent elimination half-life of teplizumab is approximately 3 days.

Special populations

Age

No clinically significant differences in the pharmacokinetics of teplizumab were observed based on age (8 to 35 years old).

Gender

No clinically significant differences in the pharmacokinetics of teplizumab were observed based on gender.

Race

No clinically significant differences in the pharmacokinetics of teplizumab were observed based on racial groups (White, Asian).

Body weight

BSA-based dosing normalises the exposure to teplizumab across body weight.

Renal impairment

No specific studies to evaluate the pharmacokinetics of teplizumab in patients with renal impairment have been performed.

Hepatic impairment

No specific studies to evaluate the pharmacokinetics of teplizumab in patients with hepatic impairment have been performed.

Paediatric population

The pharmacokinetics of teplizumab in children younger than 8 years of age have not been established.

Preclinical safety data

No studies have been performed to assess the genotoxic, including mutagenic, potential of teplizumab. As an antibody, teplizumab is not expected to interact directly with DNA. No long-term studies have been performed to assess the carcinogenic potential of teplizumab. Based on the weight of evidence assessment and the proposed long term immunomodulatory mode of action a very low potential carcinogenicity risk cannot fully be excluded.

Developmental and reproductive toxicity

Non-clinical studies conducted in mice using a surrogate antibody directed towards murine CD3 indicate direct or indirect harmful with respect to pregnancy and embryonic/foetal development.

In an embryo-foetal developmental toxicity study in pregnant mice by subcutaneous injection at dose levels of 0, 0.03, 0.3, or 20 mg/kg on gestation days 6, 10, and 14, increase in post-implantation loss occurred in the 20 mg/kg group in the presence of maternal toxicity.

In a pre- and postnatal development toxicity study in pregnant mice administered every 3 days from gestation day 6 through lactation day 19 at doses of 0, 0.3, 3, or 20 mg/kg, no maternal toxicity or increased incidence of post-implantation loss was observed. Reductions in T cell populations and increases in B cells, and a reduction in the adaptive immune response to keyhole limpet hemocyanin (KLH) were observed in the offspring on postnatal days 35 and 84 at 20 mg/kg. The surrogate antibody was present in the offspring serum at level less than 1.5% that of maternal serum at the high dose. A trend towards reduction in fertility was observed in the offspring of dams at 20 mg/kg.

Fertility and reproductive performance were unaffected in female and male mice that received a murine surrogate anti-mouse CD3 antibody administered by the subcutaneous route at doses up to 20 mg/kg.

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