Is MannKind Stock a Buy or Sell After the CEO Sold Nearly 66,000 Shares?

On Dec. 17, 2025, Michael Castagna, Chief Executive Officer of MannKind Corporation (NASDAQ:MNKD), executed an exercise and immediate sale of 65,804 common shares for a transaction value of approximately $395,482, according to the SEC Form 4 filing.

Transaction summary

Transaction value based on SEC Form 4 weighted average purchase price ($6.01); post-transaction value based on Dec. 17, 2025 market close price ($5.97).

Key questions

• How significant is the transaction relative to Mr. Castagna's recent selling activity?
  The sale of 65,804 shares is closely aligned with Mr. Castagna's median sell transaction size of 75,455 shares during the recent period, indicating the trade is representative of his established cadence as CEO.
• What impact did the transaction have on direct ownership levels?
  Mr. Castagna's direct holdings decreased from 2,570,596 to 2,504,792 shares, a 2.56% reduction, maintaining his post-transaction ownership at 0.8159% of outstanding shares.
• What is the context and structure of the transaction?
  This event involved the exercise of employee stock options for 65,804 shares, all of which were immediately sold, with no indirect ownership or related-party transfers.
• How does this activity relate to capacity and holding trends?
  The absolute size of the sale reflects a measured approach consistent with prior trades, and the declining share balance suggests that the current trade size is shaped by remaining capacity rather than a change in disposition strategy.

Company overview

* 1-year price change calculated using Dec. 17, 2025 as the reference date.

Company snapshot

• MannKind Corporation's key products include Afrezza (inhaled insulin) and Thyquidity (hypothyroidism treatment), with ongoing development of inhaled therapies for endocrine and orphan lung diseases.
• The company generates revenue primarily through the commercialization of proprietary inhaled therapeutics and strategic licensing agreements.
• Its main customers are adult and pediatric endocrinologists, healthcare providers, and patients with diabetes or rare pulmonary conditions.

MannKind Corporation is a biotechnology company specializing in the development and commercialization of inhaled therapeutic products for diabetes and rare lung diseases. The company's focus on proprietary drug delivery platforms and strategic collaborations supports its position in the biopharmaceutical sector.

MannKind's innovative approach and targeted product portfolio provide differentiation in the competitive healthcare landscape.

What this transaction means for investors

MannKind CEO Michael Castagna's sale of company shares is not a warning sign or cause for alarm. He still retained over 2.5 million shares in MannKind after the transaction. Moreover, the size of the sale was within Mr. Castagna's median sell transaction size, which suggests it was part of a pre-arranged trading plan, something many CEOs enact so that their stock sales are done independent of any material non-public information.

The sale comes at a time when MannKind shares are experiencing an upswing after hitting a 52-week low of $3.38 in August. That's because the company is on a roll.

Its third quarter financial performance was excellent, with sales of $82.1 million, up 17% over the previous year. The U.S. Food and Drug Administration accepted MannKind's application for a version of its Afrezza drug intended for children and adolescents, marking an important step in the company's attempt to open up a new market.

It also completed the acquisition of scPharmaceuticals, a key event that management believes will be a "significant expansion of our commercial capabilities and is expected to accelerate growth of our product revenues," according to Mr. Castagna.

With a P/E ratio around 60, now is a good time to sell MannKind stock, but for investors interested in buying, wait until the share price drops.

Glossary

Form 4: A required SEC filing disclosing insider transactions in a company's securities.
Option exercise: The act of converting stock options into actual company shares, typically by paying a set price.
Immediate sale: Selling shares right after acquiring them, often following an option exercise.
Direct holdings: Shares owned personally by an individual, not through trusts or other entities.
Indirect ownership: Shares held through another entity, such as a trust or family member, rather than directly.
Outstanding shares: Total shares of a company currently held by all shareholders, including insiders and the public.
Disposition: The act of selling or otherwise transferring ownership of securities.
Weighted average price: The average price per share, weighted by the number of shares traded at each price.
Cadence: The regular frequency or pattern of an insider's trading activity.
Capacity management: Adjusting the size or timing of trades based on remaining available shares or trading limits.
Proprietary: Owned exclusively by a company, often referring to unique products or technologies.
TTM: The 12-month period ending with the most recent quarterly report.

Robert Izquierdo has no position in any of the stocks mentioned. The Motley Fool has positions in and recommends MannKind. The Motley Fool has a disclosure policy.