BioMed Realty LP, an operating partnership subsidiary of San Diego-based BioMed Realty Trust Inc., plans to do a $400 million offering of senior unsecured notes.

The 2.625 percent senior notes, due in 2019, have been priced at 99.408 percent of the principal amount, to yield 2.752 percent to maturity, officials at BioMed said. The offering is expected to close April 23, and the notes will be senior unsecured obligations fully guaranteed by BioMed Realty Trust.

The operating partnership plans to use net proceeds to repay a portion of outstanding debt under its unsecured line of credit, and for other general corporate and working capital purposes, officials said in a statement.

BioMed Realty Trust (NYSE: BMR) also announced that its investment-grade corporate credit rating from Standard & Poor’s Rating Services has been upgraded from BBB- to BBB. Officials said BioMed in 2010 was the first life-sciences real estate investment trust to receive investment grade credit ratings from S&P and Moody’s Investors Service.

BioMed has since received positive outlooks from S&P in June 2013 and Moody’s in March 2014. Greg Lubushkin, the company’s chief financial officer, said the investment-grade corporate credit rating is among “key drivers of our capital strategy” and a competitive advantage in pursuing growth opportunities.

Headquartered in Rancho Bernardo, BioMed holds a U.S. and U.K. portfolio of life-science office and lab-space properties totaling about 17.3 million rentable square feet.