NELL1 and osteoporosis: We have previously demonstrated that PEGylation of NELL-1 osteogenic protein significantly enhances NELL-1 pharmacokinetics by increasing the serum half-life, allowing the protein to be administered weekly IV to treat osteoporosis in mice.10,11 The present study revealed that a weekly injection of a double-dose NELL-PEG via IP injection also successfully increases BMD and trabecular bone formation with reduced bone resorption, presenting the IP administration is an alternative and more patient-friendly approach to systemically deliver NELL-PEG for the treatment for osteoporosis.