Insiders selling shares without any recorded purchases over the last year raises caution. The alignment between management and smaller shareholders due to insider ownership is not outstanding. Caution is advised before buying shares in Blueprint Medicines due to significant selling activity.

The stock's commendable performance is tied to revenue growth. However, profitability and cash flow checks are crucial for future views. Given the strong share price momentum, the stock warrants a closer look.

Blueprint Medicines' high P/S ratio is worrisome due to its lower projected growth compared to the broader industry. If future revenues don't support this optimism, the current high P/S ratio may not be sustainable. Prices may not be reasonable unless conditions significantly improve.

Blueprint Medicines' increased debt brings a heightened risk profile due to last year's dilution in revenues and lack of profitability. Its future earnings and balance sheet health are key to assessing risk.

Significant sale by President of R&D Fouad Namouni implies shares may not be undervalued. This, along with multiple insider sales, is a potential red flag for investors.

The significant fall in both the share price and revenue of Blueprint Medicines Corporation could indicate unresolved issues within the company. The continued lack of profitability may also be a concern for long-term investors.