In a move drawing attention across the biopharmaceutical industry, the FDA recently released more than 200 complete response letters (CRLs) issued between 2020 and 2024. The agency says the goal is simple: to increase transparency and help sponsors better understand the common pitfalls that delay approvals.

This update marks a new direction. Until now, CRLs were shared only with individual product sponsors. But with so many applications facing delays due to safety concerns, trial design issues, or manufacturing problems, the FDA is betting that public access can improve learning and ultimately help drug developers reach the market more efficiently.

For sponsors and CROs, this release offers a valuable (and long overdue) opportunity to course-correct.

What is a Complete Response Letter?

A CRL isn’t a full rejection. Instead, it signals that the FDA cannot approve a drug or biologic application in its current form. The letter outlines the agency’s specific concerns, whether that’s a request for additional data, revisions to the protocol, or issues with manufacturing compliance.

According to the FDA, nearly 4 in 10 new drug applications and biologics license applications received a CRL between 2018 and 2022. While the reasons vary, the most common issues cited include:

• Gaps in safety or efficacy data
  
• Poor trial design or execution
  
• Incomplete or inadequate manufacturing information
  

In many cases, these applications weren’t far from the finish line, but they still failed to meet FDA expectations.

Transparency Gaps Have Slowed Industry Learning

For years, developers have had limited visibility into why the FDA turns down certain applications. A 2015 study found that 85% of the safety and efficacy issues cited in CRLs were never publicly disclosed by sponsors. Even when press releases were issued, they often left out critical findings. Among CRLs that cited increased mortality in trial participants, only one sponsor publicly shared that detail.

As a result, many developers have been navigating the regulatory process without full insight, repeating avoidable mistakes. The FDA’s new approach aims to change that.

What We’ve Learned From the First 200 Letters

The newly published CRLs aren’t just regulatory documents. They serve as reference points, helping sponsors see where previous submissions missed the mark. Some of the most eye-opening takeaways include:

• 48% of CRLs cited both safety and efficacy deficiencies
  
• Only 13% cited neither, meaning most applications had at least one significant issue
  
• More than 40% of CRLs that requested new clinical trials never had that requirement acknowledged in the sponsor’s press release
  

The FDA says it hopes this information will help improve submission quality and reduce common errors that delay approvals.

What This Means for Drug Developers

Regulatory delays are costly. Each round of revisions and resubmissions takes time, strains resources, and adds financial pressure. If sponsors can see where others have struggled, it’s easier to build smarter, more complete submissions from the start.

The newly released CRLs are now available on the openFDA platform. You can search by therapeutic area, application number, or year. Each letter has been redacted to protect proprietary information, but the regulatory guidance remains intact.

If your team is preparing an NDA or BLA, now is a good time to review your documentation, double-check your safety data, and revisit your trial design. With these CRLs available, there’s no need to guess what the FDA is looking for.

Moving Forward With Greater Clarity

The FDA has made it clear that more CRLs will be released in the months ahead. The agency’s hope is that increased visibility will lead to stronger applications, faster reviews, and better outcomes for patients.

While drug development is never without challenges, public access to this level of insight is a meaningful step forward. For the first time, developers can look beyond their own submissions and learn from the broader industry.

At Harbor Clinical, we help sponsors navigate these challenges with confidence. From study startup and regulatory support to safety monitoring and inspection readiness, our team is here to help your drug development efforts stay on track.

To learn more about our services, call (781) 775–0342 or email [email protected].