Long-term treatment with active Aβ immunotherapy with CAD106 in mild Alzheimer's disease.
BACKGROUND
CAD106 is designed to stimulate amyloid-β (Aβ)-specific antibody responses while avoiding T-cell autoimmune responses. The CAD106 first-in-human study demonstrated a favorable safety profile and promising antibody response. We investigated long-term safety, tolerability and antibody response after repeated CAD106 injections.


METHODS
Two phase IIa, 52-week, multicenter, randomized, double-blind, placebo-controlled core studies (2201; 2202) and two 66-week open-label extension studies (2201E; 2202E) were conducted in patients with mild Alzheimer's disease (AD) aged 40 to 85 years. Patients were randomized to receive 150μg CAD106 or placebo given as three subcutaneous (2201) or subcutaneous/intramuscular (2202) injections, followed by four injections (150 μg CAD106; subcutaneous, 2201E1; intramuscular, 2202E1). Our primary objective was to evaluate the safety and tolerability of repeated injections, including monitoring cerebral magnetic resonance imaging scans, adverse events (AEs) and serious AEs (SAEs). Further objectives were to assess Aβ-specific antibody response in serum and Aβ-specific T-cell response (core only). Comparable Aβ-immunoglobulin G (IgG) exposure across studies supported pooled immune response assessments.


RESULTS
Fifty-eight patients were randomized (CAD106, n = 47; placebo, n = 11). Baseline demographics and characteristics were balanced. Forty-five patients entered extension studies. AEs occurred in 74.5% of CAD106-treated patients versus 63.6% of placebo-treated patients (core), and 82.2% experienced AEs during extension studies. Most AEs were mild to moderate in severity, were not study medication-related and did not require discontinuation. SAEs occurred in 19.1% of CAD106-treated patients and 36.4% of placebo-treated patients (core). One patient (CAD106-treated; 2201) reported a possibly study drug-related SAE of intracerebral hemorrhage. Four patients met criteria for amyloid-related imaging abnormalities (ARIA) corresponding to microhemorrhages: one was CAD106-treated (2201), one placebo-treated (2202) and two open-label CAD106-treated. No ARIA corresponded to vasogenic edema. Two patients discontinued extension studies because of SAEs (rectal neoplasm and rapid AD progression, respectively). Thirty CAD106-treated patients (63.8%) were serological responders. Sustained Aβ-IgG titers and prolonged time to decline were observed in extensions versus core studies. Neither Aβ1-6 nor Aβ1-42 induced specific T-cell responses; however, positive control responses were consistently detected with the CAD106 carrier.


CONCLUSIONS
No unexpected safety findings or Aβ-specific T-cell responses support the CAD106 favorable tolerability profile. Long-term treatment-induced Aβ-specific antibody titers and prolonged time to decline indicate antibody exposure may increase with additional injections. CAD106 may be a valuable therapeutic option in AD.


BACKGROUND
ClinicalTrials.gov identifiers: NCT00733863, registered 8 August 2008; NCT00795418, registered 10 November 2008; NCT00956410, registered 10 August 2009; NCT01023685, registered 1 December 2009.
Department of Neurology, Indiana University School of Medicine, 355 West 16th Street, Suite 4700, Indianapolis, IN 46202 USA.
Martin R
MR
Farlow
Karolinska Institutet, Dept NVS, Center for Alzheimer Research, Division for Neurogeriatrics, Novum, Huddinge, SE-141 57 Stockholm Sweden ; Karolinska University Hospital Huddinge, Geriatric Clinic, Clinical Trial Unit, SE-141 86 Stockholm, Sweden.
Niels
N
Andreasen
Novartis Pharma AG, Basel, CH-4002 Switzerland.
Marie-Emmanuelle
ME
Riviere
Novartis Pharma AG, Basel, CH-4002 Switzerland.
Igor
I
Vostiar
Novartis Pharma AG, Basel, CH-4002 Switzerland.
Alessandra
A
Vitaliti
Novartis Pharma AG, Basel, CH-4002 Switzerland.
Judit
J
Sovago
Novartis Pharma AG, Basel, CH-4002 Switzerland.
Angelika
A
Caputo
Karolinska Institutet, Dept NVS, Center for Alzheimer Research, Division for Neurogeriatrics, Novum, Huddinge, SE-141 57 Stockholm Sweden ; Karolinska University Hospital Huddinge, Geriatric Clinic, Clinical Trial Unit, SE-141 86 Stockholm, Sweden.
Bengt
B
Winblad
Novartis Pharma AG, Basel, CH-4002 Switzerland.
Ana
A
Graf