University of Maryland BioPark leaders have their sights set on a midsize Boston company to move into the park’s third office building, possibly as anchor tenant.

Construction of the BioPark’s third multi-tenant building — 200,000 square feet of office and lab space along West Baltimore Street — hinges on nailing down an anchor tenant, or multiple companies to fill between 30 percent and 45 percent of the building, at least 60,000 square feet. BioPark leaders want to begin construction in the fall and this week made progress toward that goal, by spending time wooing their Boston belle at the BIO International Convention, which took place in Boston June 18-21.

BioPark leaders declined to identify the company, other than to say it is a Boston-based biotechnology firm that does not have any offices outside Beantown. James Hughes, the BioPark’s president, said he did not expect a final decision from the company did not expect to come home with a final decision and did not know how much of its operations the company might move to Baltimore. But, he said, “It’s looking positive.”

The BioPark’s nearness to securing a new anchor tenant is the most recent in a string of developments that show the 12-acre park is emerging from a period of sluggish growth in a poor economy. A $200 million cancer treatment center will be completed in 2014 and is expected to treat up to 2,000 patients a year and employ about 185 people, beginning in 2015.

A study is underway for a 100-room hotel, which would be used for patients and their families who need lodging for an extended period of time. The park’s existing two buildings are almost to capacity, with several new tenants unveiled in recent months. The BioPark announced two more tenants June 19.

Leaders are focused on reeling in tenants for the new building to keep up that momentum and solidify Baltimore as a leading biotechnology market.

“Outside of Maryland, people know Baltimore as the location of Johns Hopkins and the University of Maryland Medical Center, but they don’t really think of it as a biotech center,” Hughes said. “We’re trying to expand the image of Baltimore as a place for biotech companies to locate.”

The new companies announced June 19 have international ties, which is indicative of the biopark’s recruitment strategy. Biogen Diagnostics Ltd. is based in the United Kingdom and Global Scientific Solutions for Health Inc. operates laboratories in Southeast Asia and Africa. BioPark leaders are going after both homegrown companies that operate primarily in the mid-Atlantic region, as well as companies with an international scope, said Jane Shaab, the BioPark’s executive director.

Attracting companies with tentacles overseas can benefit the other BioPark companies by giving them access to markets they otherwise would not consider, she said.

But in an industry in which Baltimore must compete with such biotech giants as Silicon Valley and Boston — not to mention Montgomery County’s Interstate 270 corridor to the south — keeping business local may be a better bet, said Ellen Hemmerly, president of bwtech@UMBC Research and Technology Park. The University of Maryland, Baltimore County’s incubator primarily hosts early stage and startup biotech companies.

“Maryland certainly offers some of the best talent, best universities, best research,” Hemmerly said. “We’re not necessarily the cheapest place to do business.”

If companies are going to pay top dollar to set up shop somewhere, they may opt for a more mature market, Hemmerly said. But for many companies, home base is a personal decision. So by that logic, creating a nesting ground for companies run by Maryland natives is a smart move. The state has made moves in that direction, with its biotech tax credit and push for tech transfer among research universities.

“Our success is probably going to lie more with growing our own companies than bringing companies from outside the state and region,” she said.

A desire to grow its business near where it was born prompted Vigilant Bioservices to seek out a spot at the UM BioPark. The company, which stores critical materials such as tissue and cell lines, was founded in 2009 in Columbia and relocated to Baltimore last October.

The company has already made new business connections, accrued clients and gained more name recognition, which managing partner Jeff Lange credits to being part of the BioPark community. Lange and his business partners looked at cheaper options, but decided the network the BioPark could offer outweighed any monetary concerns.

“We’re banking on the potential,” he said.