Michael Clark is the new president and executive director of the Nonprofit Coordinating Committee (NPCC) of New York, an umbrella organization for more than 1,300 nonprofits. Clark has served as president of Citizens for NYC, a community group, for 18 years. He will succeed Jon Small on May 2, when Small returns to his law career after leading the organization for five years.

Tom Gerety, executive director of the Brennan Center for Justice at the New York University School of Law, is leaving to resume his academic career, including writing books and teaching. The organization is conducting a search for his successor.

HIV/AIDS Services at the New York City Department of Health and Mental Hygiene (DOHMH) welcomes Scott Kellerman. Kellerman, who took the reins in early March, is in charge of implementing the city’s HIV/AIDS Continuum of Care plan. He also oversees more than $200 million in funding for related program contracts. Before joining DOHMH, Kellerman worked for several government HIV/AIDS programs, including the Division of HIV/AIDS Prevention at the federal Centers for Disease Control and Prevention.

Mothers on the Move (MOM), a South Bronx social justice organization, and the nonprofit Northwest Bronx Community and Clergy Coalition (NWBCCC), both picked up new executive directors. James Mumm, codirector of MOM, will become the head of NWBCCC in April. His codirector, Wanda Salaman, will become head of MOM. Departing NWBCCC executive director Mary Dailey will be a lead organizer with the Center for Community Change, coordinating national campaigns.

Joseph Semidei became executive director and CEO of St. Christopher, Inc. on March 14. The Westchester-based child welfare agency’s reputation has been tarnished amid a scandal over forged documents that led to the loss of city contracts and the resignation of former director Louis Medina. Previously, Semidei was deputy executive director of the Committee for Hispanic Children and Families and held senior positions in the New York City Department of Mental Health, Mental Retardation and Alcoholism Services; and the state’s Division of Family and Children Services.

Phaedra Thomas, former director of the Red Hook and Gowanus programs of the Southwest Brooklyn Industrial Development Corporation, was promoted to executive director, replacing Leah Archibald, who left to serve as director of marketing at the Industrial and Technology Assistance Corporation. A native of Brooklyn, Thomas served as director of the Red Hook Office of the Southwest Brooklyn Local Development Corporation for four years before joining SBIDC.