App security is unique within the IT realm as it encompasses the entire gamut of security, from  communication, data, and networks to the devices used for working with the applications. IT admins face steep challenges when it comes to applications, from ensuring containerization, data encryption, and application white listing to establishing a secure channel for apps to access sensitive business data. These challenges are exacerbated by the use of multiple device types, multiple platforms, and multiple manufacturers.
Unified endpoint management is probably the best way to achieve optimal app security. This would include measures like containerization to ensure corporate data gets sandboxed into separate containers, preventing users from accessing data they are not authorized to see. This is especially useful in case of mobile devices, the device of choice for remote users.
It's also important to secure data using common encryption technologies such as FileVault and BitLocker. When you encrypt corporate data on work and personal machines, any the impact of any unauthorized access or data theft is greatly minimized because the data is essentially useless.
With organizations across the globe witnessing a spike in remote users, there are cases where apps need to access corporate data from outside the corporate network. Setting up dedicated app-specific VPNs ensures a secure channel for corporate data access every time the user accesses the app.
App blacklisting ensures any unauthorized app gets automatically removed from the devices and prevents their subsequent installation. Gatekeeper is often used to prevent app installation from unapproved sources.
All of these tactics are of little use, however, without a dynamic app management policy,  drafted after comprehensively understanding end user needs and carefully monitoring the enterprise environment. Draft that policy and educate your uses so that they adhere to it.