Pharmacotherapeutic Group: Selective immunosuppressants.
ATC Code: L04AA34.
Pharmacology: Pharmacodynamics: Mechanism of Action: Alemtuzumab, is a recombinant DNA-derived humanised monoclonal antibody directed against the 21-28 kD cell surface glycoprotein CD52. Alemtuzumab is an IgG1 kappa antibody with human variable framework and constant regions, and complementary-determining regions from a murine (rat) monoclonal antibody. The antibody has an approximate molecular weight of 150 kD.
Alemtuzumab binds to CD52, a cell surface antigen present at high levels on T (CD3+) and B (CD19+) lymphocytes, and at lower levels on natural killer cells, monocytes, and macrophages. There is little or no CD52 detected on neutrophils, plasma cells, or bone marrow stem cells. Alemtuzumab acts through antibody-dependent cellular cytolysis and complement-mediated lysis following cell surface binding to T and B lymphocytes.
The mechanism by which LEMTRADA exerts its therapeutic effects in MS is not fully elucidated. However, research suggests immunomodulatory effects through the depletion and repopulation of lymphocytes, including: Alterations in the number, proportions, and properties of some lymphocyte subsets post-treatment;
Increased representation of regulatory T cell subsets;
Increased representation of memory T- and B-lymphocytes;
Transient effects on components of innate immunity (i.e., neutrophils, macrophages, NK cells).
The reduction in the level of circulating B and T cells by LEMTRADA and subsequent repopulation, may reduce the potential for relapse, which ultimately delays disease progression.
Pharmacodynamic Effects: LEMTRADA depletes circulating T and B lymphocytes after each treatment course with the lowest observed values occurring 1 month after a course of treatment (the earliest post-treatment time point in phase 3 studies). Lymphocytes repopulate over time with B-cell recovery usually completed within 6 months. CD3+ and CD4+ lymphocyte counts rise more slowly towards normal, but generally do not return to baseline by 12-months post-treatment. Approximately 40% of patients had total lymphocyte counts reaching the lower limit of normal (LLN) by 6 months after each treatment course, and approximately 80% of patients had total lymphocyte counts reaching the LLN by 12 months after each course.
Neutrophils, monocytes, eosinophils, basophils, and natural killer cells are only transiently affected by LEMTRADA.
Clinical Efficacy and Safety: The safety and efficacy of LEMTRADA were evaluated in 3 randomised, rater-blinded, active-comparator clinical trials and one uncontrolled, rater-blinded extension study in patients with RRMS.
For studies 1 and 2, Study design/demographics and results are shown in Tables 1 and 2 respectively. (See Tables 1 and 2.)
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See Figure.
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Relapse severity: In alignment with the effect on relapse rate, supportive analyses from Study 1 (CAMMS323) showed that LEMTRADA 12 mg/day led to significantly fewer LEMTRADA treated patients experiencing severe relapses (61% reduction, p=0.0056) and signficantly fewer relapses that led to steroid treatment (58% reduction, p<0.0001) compared to IFNB-1a.
Supportive analyses from Study 2 (CAMMS32400507) showed that LEMTRADA 12 mg/day led to significantly fewer LEMTRADA-treated patients experiencing severe relapses (48% reduction, p=0.0121), and significantly fewer relapses that led to steroid treatment (56% reduction, p<0.0001) or to hospitalization (55 % reduction, p=0.0045) compared to IFNB-1a.
Sustained reduction of disability (SRD): Time to onset of SRD was defined as a decrease of at least one point on the EDSS from a baseline EDSS score ≥ 2 that was sustained for at least 6 months. SRD is a measure for sustained disability improvement. 29% of patients treated with LEMTRADA reached SRD in study 2, while only 13% of subcutaneous IFNB- 1a treated patients reached this endpoint. The difference was statistically significant (p=0.0002).
Study 3 (phase 2 study CAMMS223) evaluated the safety and efficacy of LEMTRADA in patients with RRMS over the course of 5 years. Patients had an EDSS from 0-3.0, at least 2 clinical episodes of MS in the prior 2 years, and ≥1 gadolinium-enhancing lesion at study entry. Patients had not received prior therapy for MS. Patients were treated with LEMTRADA 12 mg/day (N=108) or 24 mg/day (N=108) administered once per day for 5 days at Month 0 and for 3 days at Month 12 or subcutaneous IFNB-1a 44 μg (N=107) administered 3 times per week for 3 years. Forty-six patients received a third course of LEMTRADA treatment at 12 mg/day or 24/mg day for 3 days at Month 24.
At 3 years, LEMTRADA reduced the risk of 6-month CDW by 76% (hazard ratio 0.24 [95% CI: 0.110, 0.545], p<0.0006) and reduced the ARR by 67% (rate ratio 0.33 [95% CI: 0.196, 0.552], p<0.0001) as compared to subcutaneous IFNB-1a. Alemtuzumab 12 mg/day led to significantly lower EDSS scores (improved compared to baseline) through 2 years of follow up, compared with IFNB-1a (p<0.0001).
Long-term efficacy data: Study 4, provides efficacy data for up to 6 years from entry into Studies 1 and 2. Of patients treated with LEMTRADA 12 mg in Studies 1 and 2, 91.8% entered Study 4.
Table 3 presents the key clinical and MRI outcomes in Study 4 for LEMTRADA 12 mg patients from Studies 1 and 2. (See Table 3.)
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The ARR of patients originally treated with LEMTRADA remained low throughout Study (Table 3), with a high percentage of patients relapse-free in each year of follow-up. Most patients never experienced confirmed disability worsening. Mean disability scores were stable or improved in most years. Through 6 years from first LEMTRADA treatment, 42.5% and 32.7% of patients from Studies 1 and 2, respectively, reached CDI. Patients also continued to show a low risk of forming new T2 lesions or gadolinium enhancing lesions in each year of follow-up. The T2 lesion volume remained lower throughout the follow-up period than prior to initial LEMTRADA treatment (median percent change at Year 6, -0.1 and -8.5 for Study 1 and 2 populations, respectively), with only small changes from year to year. The median annual percent change (reduction) in brain parenchymal fraction was lower during the extension period than in the prior studies. Approximately half (51.2%) of patients initially treated with LEMTRADA 12 mg/day in Study 1 or 2 who enrolled in Study 4 had received only the initial 2 courses of LEMTRADA and no other disease modifying treatment throughout 6 years of follow-up.
These results demonstrate durable efficacy of LEMTRADA on reducing the risk of MS relapse, suppressing the formation of new MS lesions, slowing brain volume loss (atrophy) and disability worsening in the absence of continuous treatment.
Additional as-needed treatment: In study 4, 40% of the patients initially treated with LEMTRADA 12 mg/day in Study 1 or 2 received additional courses upon documented evidence of MS disease activity (relapse and/or MRI) and the treating physician's decision to retreat. Additional course(s) of LEMTRADA were administered at 12 mg/day for 3 consecutive days (36 mg total dose) at least 12 months after the prior treatment course. Efficacy results in these patients, by treatment course, are presented in Table 4. (See Table 4.)
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Relapse rate, MRI activity and mean EDSS score all improved in the year both following a third or fourth LEMTRADA treatment course when compared with outcomes in the preceding year (Table 4).
These data demonstrate that patients with MS disease activity following a prior LEMTRADA treatment course can achieve clinical improvement on clinical and MRI measures (reduced ARR, decreased lesions and stabilization of disability) after additional LEMTRADA treatment courses.
The benefits and risks of 5 or more treatment courses have not been fully established, but results suggest that the safety profile does change with additional courses. If additional treatment courses are to be given they must be administered at least 12 months after the prior course.
Pharmacokinetics: The pharmacokinetics of LEMTRADA were evaluated in a total of 216 patients with RRMS who received intravenous infusions of either 12 mg/day or 24 mg/day for 5 consecutive days, followed by 3 consecutive days 12 months following the initial treatment course. Serum concentrations increased with each consecutive dose within a treatment course, with the highest observed concentrations occurring following the last infusion of a treatment course. Administration of 12 mg/day resulted in a mean C
max of 3014 ng/ml on Day 5 of the initial treatment course, and 2276 ng/ml on Day 3 of the second treatment course. The alpha half-life approximated 4-5 days and was comparable between courses leading to low or undetectable serum concentrations within approximately 30 days following each treatment course.
Alemtuzumab is a protein for which the expected metabolic pathway is degradation to small peptides and individual amino acids by widely distributed proteolytic enzymes. Classical biotransformation studies have not been conducted.
Conclusions cannot be made with available data on the effect of race and gender on the pharmacokinetics of LEMTRADA. The pharmacokinetics of LEMTRADA has not been studied in patients aged 55 years and older.
Toxicology: Preclinical Safety Data: Carcinogenesis and mutagenesis: There have been no studies to assess the carcinogenic or mutagenic potential of alemtuzumab.
Fertility and reproduction: Treatment with intravenous alemtuzumab at doses up to 10 mg/kg/day, administered for 5 consecutive days (AUC of 11.8 times the human exposure at the recommended daily dose) had no effect on fertility and reproductive performance in male huCD52 transgenic mice. The number of normal sperm was significantly reduced (<10%) relative to controls and the percent abnormal sperm (detached heads or no heads) were significantly increased (up to 3%). However, these changes did not affect fertility and were therefore considered to be non-adverse.
In female mice dosed with intravenous alemtuzumab up to 10 mg/kg/day (AUC of 7.9 times the human exposure at the recommended daily dose) for 5 consecutive days prior to cohabitation with wild-type male mice, the average number of corpora lutea and implantation sites per mouse were significantly reduced as compared to vehicle treated animals. Reduced gestational weight gain relative to the vehicle controls was observed in pregnant mice dosed with 10 mg/kg/day.
A reproductive toxicity study in pregnant mice exposed to intravenous doses of alemtuzumab up to 10 mg/kg/day (AUC 4.1 times the human exposure at the recommended dose of 12 mg/day) for 5 consecutive days during gestation resulted in significant increases in the number of dams with all conceptuses dead or resorbed, along with a concomitant reduction in the number of dams with viable foetuses. There were no external, soft tissue, or skeletal malformations or variations observed at doses up to 10 mg/kg/day.
Placental transfer and potential pharmacologic activity of alemtuzumab were observed during gestation and following delivery in mice. In studies in mice, alterations in lymphocyte counts were observed in pups exposed to alemtuzumab during gestation at doses of 3 mg/kg/day for 5 consecutive days (AUC 1.0 times the human exposure at the recommended dose of 12 mg/day). Cognitive, physical, and sexual development of pups exposed to alemtuzumab during lactation were not affected at doses up to 10 mg/kg/day alemtuzumab.