The journey from concept to approved drug for MannKind Corp.'s Afrezza inhaled insulin is one beset by multiple regulatory setbacks that saw the company - the brainchild of serial entrepreneur, Chairman and CEO Alfred Mann - burn through more than $1.6 billion in cash over the past 12 years.

Indeed, the company has sustained itself with Mann's deep pockets. Mann and his entities owned 40% of MannKind as of March 21. And as of March 31, the company also owed the Mann Group $49.5 million under a loan arrangement.