Multimeric fusion proteins of an Ig-like domain of Flt-1 are rendered functional by inclusion of a linker moiety. Vectors encoding the fusion proteins and host cells expressing the fusion proteins can be used therapeutically to block neovascularization in individuals with pathological conditions related to neovascularization. Such conditions include age-related macular degeneration, cancer, psoriasis, proliferative diabetic retinopathy, asthma, uveitis, osteoarthritis, and rheumatoid arthritis. The same means of multimerization used for an Iglike domain of Flt-1, i.e., a linker and a multimerization domain, can be used for other polypeptides, including extracellular receptors, antibody variable regions, cytokines, chemokines, and growth factors.