AL 003, a monoclonal antibody targeting Siglec-3 (CD33) is being developed by Alector in collaboration with AbbVie for the treatment of Alzheimer's disease. Early clinical development is underway in Australia and preclinical research is ongoing in the US.
Siglec-3, is a transmembrane glycoprotein which is expressed on the surface of myeloid progenitor cells, mature monocytes and macrophages. Siglec-3 contains putative immunoreceptor tyrosine based inhibitory motifs which inhibit cellular activity. Upon activation, Siglec-3 constitutively repress monocyte-derived pro-inflammatory cytokines as well as microglia and their ability to dispose of the accumulated debris which cause Alzheimer's disease.
AL 003 has emerged from a research programme of Alector in collaboration with AbbVie on antibody therapeutics [see Adisinsight drug profile 800050570].
In October 2017, AbbVie entered into a global research and development agreement with Alector, to develop and commercialise immune therapies for the treatment of Alzheimer's disease and other neurodegenerative disorders. Under the terms of the agreement, AbbVie and Alector have agreed to research a portfolio of antibody targets and AbbVie has an option to global development and commercial rights to two targets which include a triggering receptor expressed on myeloid cells 2 (TREM2) and Siglce-3 receptor. Alector will conduct exploratory research, drug discovery and development for lead programs up to the conclusion of the proof of concept studies. Upon exercising the option, AbbVie will lead development and commercialisation activities. Alector and AbbVie will co-fund development and commercialisation and will share global profits equally. Alector will receive a $US205 million upfront payment and a potential, future equity investment of up to $US20 million.  
Key Development Milestones
Alector, in March 2019, initiated a phase I trial of AL 003 in healthy volunteers and in patients with mild to moderate Alzheimer's disease (AL003-1, NCT03822208). The randomised, double-blind, placebo-controlled, dose escalation, first in human (FIH) trial is designed to evaluate the safety, immunogenicity, tolerability, pharmacokinetics and pharmacodynamics of AL 003  .
In July 2018, Alector secured $US133 million in Series E financing round. The company has previously raised $US282 million. The company expect to utilize the proceeding from the financing to advance Alector’s clinical programs and expand the company’s discovery platform  .
Alector owned four patent families directed to the SIGLEC 3 program, which includes 3 pending US non-provisional patent applications, 1 pending US provisional patent application, and multiple pending foreign patent applications covering the compositions and uses of our SIGLEC 3 program product candidates. 2 patent families are expected to expire in 2036, the third patent family in 2038, and the fourth patent family, assuming that the necessary non-provisional patent applications are timely filed and all other applicable requirements are satisfied for the US provisional patent application, in 2039, in all cases excluding any patent term adjustments and any patent term extensions  .