If you’re just concatenating strings, you can use compile time string concatenation:
#ifdef DEBUG
#define kAPIEndpointHost @"http://example.dev"
#else
#define kAPIEndpointHost @"http://www.example.com"
#endif
#define kAPIEndpointLatest (kAPIEndpointHost @"/api/latest_content")
#define kAPIEndpointMostPopular (kAPIEndpointHost @"/api/most_popular")