Aileron Therapeutics Inc., a Cambridge biopharmaceutical company, said Monday that it has secured the second tranche in its Series D financing, bringing the total round to $42 million.

Current investors Apple Tree Partners, Excel Venture Management, Lilly Ventures, Novartis Venture Funds, Roche Venture Fund, and SR One participated in the round, Aileron said in a press release.

The payment of the second tranche was based on the successful progression through preclinical studies of Aileron’s lead Stapled Peptide drug, ALRN-5281.

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“These proceeds will allow us to advance ALRN-5281 through Phase 1 development and continue to develop our pipeline of Stapled Peptide drugs,” Joseph A. Yanchik III, company president and chief executive, said in a statement.

ALRN-5281 is a proprietary agonist for treating orphan endocrine disorders, including adult growth hormone deficiency and HIV lipodystrophy, as well as broader patient populations involving a wide variety of metabolic/endocrine disorders.

Aileron seeks to develop stapled peptide drugs that capitalize on 25 years of genetic research to attack the key drivers of complex diseases such as cancer, metabolic and endocrine conditions, and inflammation.