How to Become a Principal Investigator in Clinical Trials

The global count of active clinical trial investigators dropped from roughly 128,303 in 2017-18 to approximately 116,948 in 2023-24, a decline of nearly 10% in six years, according to proprietary GlobalData analysis cited in a 2025 Clinical Trials Arena sponsored report [1]. Trial site coordinators fell even more sharply over the same period, from 56,036 to 40,472 [1]. That contraction is happening while sponsor demand for trial sites and qualified investigators remains substantial across therapeutic areas. For qualified clinicians and researchers willing to take on the regulatory and operational weight of the role, that combination suggests real opportunity.

Becoming a principal investigator (PI) is not a single credentialing event. It is a progression through clinical experience, regulatory training, site infrastructure, and sponsor relationships. Done in the right order, each stage builds on the last. This guide walks through that sequence, with attention to the regulatory standards that govern the role and the operational realities that sponsors evaluate when selecting investigators for new studies.

What a Principal Investigator Actually Does

Before addressing the path to the role, it is worth being precise about what a PI is legally responsible for, because the scope is broader than many clinicians expect.

Under 21 CFR Part 312, which governs investigational new drug applications in the United States, the investigator is accountable for ensuring that a clinical investigation is conducted according to the signed investigator statement, the investigational plan, and all applicable regulations [2]. That accountability includes protecting the rights, safety, and welfare of every participant enrolled at the site, and controlling the investigational product throughout the study [2]. Under 21 CFR 312.60, these obligations cannot be fully contracted away: a PI may assign specific tasks to sub-investigators and study coordinators, but personal oversight of the investigation at the site remains with the signing investigator [2] [4].

In practice, this means a PI must ensure that the requirements relating to obtaining informed consent under 21 CFR Part 50 are met for every participant; must supervise protocol execution; must assess and report adverse events and serious adverse events to the sponsor; must maintain source documents and case report forms in inspection-ready condition; must manage the investigational product per protocol requirements; and must communicate with the sponsor's medical monitor and the institutional review board (IRB) throughout the study [2] [4]. The FDA may inspect clinical investigator sites under authority granted by 21 CFR 312.68 and 21 USC 374, with the goal of verifying compliance with regulations governing investigational products and human subject protections [3].

The regulatory pathway to the PI role in the United States involves two distinct steps: selection by the study sponsor under 21 CFR 312.53, and IRB review and approval of the research [2]. The sponsor selects the investigator based on qualifications; the IRB reviews the research protocol and assesses whether the investigator and site are suitable to conduct the study. Neither step is automatic, and both require demonstrated qualifications and site readiness.

Step 1: Meet the Educational and Licensing Baseline

The FDA does not mandate a specific degree for clinical trial investigators. The regulations at 21 CFR 312.53(a) require only that a sponsor "select investigators qualified by training and experience as appropriate experts to investigate the drug" [2]. In practice, sponsors of industry-sponsored drug trials commonly expect physician PIs (MDs or DOs) with relevant specialty certification, reflecting the requirement that the person accountable for participant safety assessments have appropriate clinical training and prescribing authority. PharmDs, PhDs with clinical research experience, and in some trial types, advanced practice providers including nurse practitioners and physician assistants, are also eligible when the sponsor determines that their qualifications are appropriate and the IRB concurs [5].

One factor that shapes sponsor decisions on non-physician PIs: when a non-physician serves in the role, sponsors and protocols commonly require that a licensed physician be identified and available to assess participant safety events that require medical judgment. The extent of that physician involvement depends on the study type, the therapeutic area, and the nature of study procedures. Aspiring PIs who are not physicians should discuss these requirements explicitly with potential sponsors during feasibility conversations.

What sponsors actually evaluate when reviewing educational qualifications is whether the investigator's clinical background is relevant to the therapeutic area. A neurologist applying to serve as PI on a Phase II Alzheimer's trial will face a different set of questions than a cardiologist applying for the same role. Specialty alignment matters because the PI must be able to personally evaluate participant safety events and make judgment calls that require domain expertise.

Step 2: Accumulate Sub-Investigator Experience

The fastest route into a PI role runs through the sub-investigator position. A sub-investigator, as defined in ICH E6(R3) Section 1.34, is any individual member of the clinical study team designated and supervised by the investigator to perform critical study-related procedures or to make important study-related decisions, including associates, residents, and research fellows [6]. The CFR carries its own parallel definition at 21 CFR 312.3(b): in a team investigation, the investigator is the responsible leader and every other team member is a sub-investigator.

Serving as a sub-I in a functioning trial gives a future PI direct exposure to the operations that are easiest to underestimate from the outside: source documentation practices, electronic case report form entry, protocol deviation assessment, monitoring visit preparation, drug accountability logs, and the communication cadence with sponsors and CROs. These are the same systems a new PI will be responsible for building and maintaining at their own site.

ACRP has noted that some sub-investigators are licensed practitioners who either were PIs in a prior study or fully meet the qualifications to be one, and that these individuals are appropriate candidates for delegation of significant responsibilities by the current PI [7]. Taking advantage of that delegation deliberately, by asking the current PI to assign eligibility reviews, adverse event narratives, or investigator meeting presentations, compresses the learning curve considerably.

The appropriate amount of sub-investigator experience before pursuing a PI role depends on individual circumstances: the complexity of the therapeutic area, the sponsor's expectations, and the depth of exposure gained during that experience. Meaningful participation across the full study lifecycle, from startup through close-out on at least one trial, provides the practical foundation that sponsors and site selection teams typically look for. Sponsors assess this during feasibility review based on the investigator's CV and documented history, rather than applying a universal minimum.

Step 3: Complete GCP Training and Targeted Certification

GCP training is required by many institutional research policies and commonly specified in sponsor study agreements. It also carries regulatory force in the European Union under the Clinical Trials Regulation (EU CTR No. 536/2014). In the United States, FDA regulations at 21 CFR Parts 50, 56, and 312 require investigators to be qualified and studies to be conducted in accordance with GCP standards, but those regulations do not specify a universal certificate or a fixed renewal interval. What constitutes adequate GCP training varies by institution, sponsor contract, and the specific regulatory context of each study.

The underlying GCP standard underwent a significant update when ICH E6(R3) was finalized at ICH Step 4 in January 2025 and subsequently adopted by the FDA in September 2025 [8]. The EMA had already required compliance for trials conducted in the European Union beginning July 23, 2025 [9]. Any training based exclusively on E6(R2) curriculum should be assessed against the new guidance, which introduces substantive changes to risk-proportionate oversight, quality-by-design frameworks, and decentralized trial governance [8]. Individual sponsors may require updated training explicitly; investigators should check contract language and institutional requirements for each study.

The standard entry point for GCP training in the United States is the CITI Program, which is commonly used by academic institutions and sponsors. For aspiring PIs, GCP training can be supplemented with targeted professional certification. The Association of Clinical Research Professionals (ACRP) offers the Certified Principal Investigator (CPI) credential. To be eligible, candidates must have 3,000 hours of verifiable clinical research work experience along with a doctorate-level degree (MD, DO, PhD, PharmD, DNP, DDS, or equivalent); licensed physician assistants, nurse practitioners, and sub-investigators who have served in a PI role are also eligible under defined conditions [10]. Regardless of degree path, candidates must provide documentation of employment as a PI or sub-investigator for at least two of the most recent five years [10]. ACRP's certification period is two years, requiring 24 points of continuing education and activities for renewal. The Society of Clinical Research Associates (SOCRA) offers the Certified Clinical Research Professional (CCRP) credential, which covers investigators, coordinators, monitors, and managers in a single cross-functional certification and requires two years of full-time experience, or 3,500 hours of part-time experience, during the prior five years [11]. SOCRA's certification period is three years, requiring 45 hours of continuing education for renewal [11].

Certification is not legally required to serve as a PI, but it signals to sponsors that the investigator has met a recognized baseline of professional competency and understands the GCP framework the study operates under. ACRP's Functional Competency Guidelines for Principal and Sub-Investigators provide a publicly available framework that also serves as useful self-assessment for anyone preparing for the role [12].

Step 4: Establish or Join a Research Site

A PI cannot operate in a vacuum. The role requires infrastructure: a qualified and trained study team, appropriate physical space and equipment, access to a functioning electronic data capture (EDC) system (typically specified or provided by the sponsor for each study), SOPs governing every critical trial process, and policies for investigational product handling and storage [13].

Aspiring PIs have two practical options. The first is to affiliate with an existing research site, either at an academic medical center, a community hospital with an active research program, or a dedicated clinical research site or site management organization (SMO). This route offers immediate access to regulatory infrastructure, an existing relationship with IRBs, and a sponsor network that the site has already developed. The tradeoff is reduced autonomy and, typically, a more structured negotiation process for PI compensation and study allocation.

The second option is establishing an independent clinical trial site, a path increasingly taken by physicians in private practice. A 2025 paper published in Contemporary Clinical Trials Communications (PMID 41142039) describes the requirements for this pathway, including adequate physical space, calibrated laboratory equipment, secure investigational product storage, trained study staff, an established relationship with an IRB, and written SOPs governing every critical study function [13]. The specific staffing composition, from clinical research coordinators to regulatory specialists, varies with the site's trial volume, therapeutic area, and resources. Site startup costs depend heavily on existing infrastructure; regulatory preparation, personnel training, technology, IRB fees, and equipment can collectively represent a substantial upfront investment that should be planned for before a sponsor agreement is signed [14].

Regardless of which path a PI takes, one principle from Sramek et al. applies to both: sponsor trust is built through performance, and early execution on a first study determines whether additional protocols follow [13].

Step 5: Complete Regulatory Onboarding Before Enrollment Begins

Certain conditions must be in place before any participant can be enrolled at a site. While many startup activities, including contract negotiation, staff training, system access setup, and document preparation, can proceed in parallel, enrollment itself is contingent on specific authorization steps being completed.

FDA Form 1572. For trials conducted under an IND, no investigator may participate until they have submitted a completed, signed Form 1572 to the study sponsor [2]. The Form 1572 is the investigator's formal statement of commitment to conducting the study in accordance with the protocol and all applicable FDA regulations. The investigator submits this form to the sponsor, not directly to the FDA; the sponsor retains it as a required record [15]. In common practice, sponsors often include Form 1572 information in IND submissions to satisfy related requirements under 21 CFR 312.23(a)(6), but this is a sponsor decision, not a universal filing obligation for the investigator [15] [17]. By signing Form 1572, the PI commits to personally conducting or supervising the investigation, following the IRB-approved protocol, ensuring informed consent requirements under 21 CFR Part 50 are met, reporting adverse events to the sponsor, and maintaining records available for FDA inspection [2] [4].

The form lists sub-investigators by name under 21 CFR 312.53(c)(1)(viii), but listing does not transfer the PI's overall accountability to those individuals [15]. As established by 21 CFR 312.60, the PI may delegate specific study tasks to qualified sub-investigators, but overall responsibility for the conduct of the investigation at the site remains with the signing investigator [2].

IRB approval. For FDA-regulated IND studies, no site may begin enrolling participants without prior IRB review and approval of the research [16]. Under 21 CFR 312.66, the investigator must assure the sponsor that an IRB will be responsible for initial and continuing review and approval of the study, and must promptly report any changes in research activity or unanticipated problems to the IRB [2]. IRB review timelines vary materially by institution and review type; this timeline should be factored into startup planning from the moment a feasibility questionnaire is submitted, since enrollment cannot begin until approval is in hand.

Financial disclosure. Under 21 CFR Part 54, investigators must disclose financial interests that could affect the objectivity of the research [16]. This includes, for covered studies, equity interests exceeding $50,000 in a publicly traded sponsor or any equity in a non-publicly traded sponsor [16]. Disclosures must be updated during the study and for one year after completion [2].

Delegation log. Before a team member performs a delegated significant trial activity, the PI should document that assignment and confirm the individual's qualifications and training for the task. ICH E6(R3) formalizes expectations around delegation documentation, and the delegation log is among the first records a clinical research associate (CRA) will review during a monitoring visit [8].

Step 6: Secure the First Study and Build a Sponsor Track Record

With site infrastructure in place and enrollment prerequisites met, the next challenge is securing that first protocol. Sponsors and CROs select sites through a formal feasibility assessment that evaluates patient population access, investigator qualifications, site infrastructure, and past performance history [13] [18]. For a site with no prior performance record, the assessment relies heavily on the PI's credentials, the depth of the patient population the site can access, and the strength of the site's documented operational systems.

Several practical approaches help first-time PIs break into sponsor selection. Registering the site with clinical trial matching platforms and sponsor-maintained investigator databases increases visibility to CROs conducting outreach for feasibility questionnaires. Joining professional organizations such as ACRP or SOCRA provides access to chapter meetings where sponsor and CRO representatives actively recruit new sites, particularly for therapeutic areas experiencing enrollment challenges.

Starting with smaller Phase II or observational studies before pursuing large Phase III oncology or rare disease protocols is operationally sensible. The regulatory complexity and enrollment expectations of late-phase pivotal trials require site experience to execute without deviations. A Phase II study completed with clean data and on-time enrollment creates the performance record that sponsors review when selecting sites for larger programs.

Once enrolled in a first study, execution quality determines everything that follows. According to WCG's 2024 Clinical Research Site Challenges Report, 72% of sponsors surveyed identified improved site training as the factor most likely to improve site performance [18]. Sites that build systems for clean documentation, responsive communication, and consistent enrollment tracking differentiate themselves in an environment where sponsors track site-level metrics across their portfolio.

Regulatory and Documentation Considerations

The full body of applicable regulations for PIs extends well beyond FDA Form 1572. The primary regulatory framework includes 21 CFR Part 11 (electronic records and signatures, where applicable to covered systems), 21 CFR Part 50 (protection of human subjects and informed consent), 21 CFR Part 54 (financial disclosure), 21 CFR Part 56 (IRBs), and 21 CFR Part 312 (IND applications for drugs and biologics) [2] [16]. For medical device trials, the governing regulation is 21 CFR Part 812, which requires a signed investigator agreement including the PI's CV and a statement of relevant experience, rather than Form 1572 [4].

ICH E6(R3), adopted in 2025, introduces changes that PIs should understand before their next study. The updated guidance places greater emphasis on quality-by-design, encouraging investigators to participate in identifying and mitigating risks to trial quality from the earliest stages of study planning [8]. It formalizes expectations around decentralized trial activities and requires that oversight processes be genuinely risk-proportionate, meaning that documentation and monitoring decisions should be calibrated to the actual risks posed by each trial activity, not applied uniformly [8]. Inspection criteria will likely evolve accordingly, with increased focus on whether risk frameworks were meaningfully implemented rather than formally completed [8].

During FDA BIMO inspections, examiners verify investigators' compliance with the recordkeeping obligations established in 21 CFR Part 312 [2] [3], including case-history documentation, informed consent records, investigational product disposition, and protocol adherence. These are compliance areas where gaps are avoidable with SOPs that are tested before study start rather than assembled after a monitoring visit flags a problem.

AI and Automation in Investigator Operations

AI tools are reaching site operations in a few specific ways. Patient pre-screening applications that integrate with electronic health records can help investigators identify potentially eligible participants earlier in a recruitment window, reducing the time coordinators spend on manual chart review. Document review tools can flag potential inconsistencies in informed consent forms, delegation logs, and source document templates before they reach a monitoring visit. Whether and how these tools affect screen failure rates or deviation rates at a given site depends on the tool, the study design, and how it is implemented.

These applications are useful when validated for the clinical context in which they are deployed, governed by the PI's oversight framework, and documented appropriately in the site's SOPs. An AI-assisted eligibility summary does not substitute for the PI's clinical assessment. A template-checking tool does not replace trained staff judgment during a monitoring review. The practical contribution of these tools is in reducing routine administrative burden and surfacing issues for human review, not in removing the investigator from any clinical or regulatory decision point.

Protocol and site documentation preparation is one area where AI-assisted generation may help reduce the time between protocol receipt and startup-ready documentation. Writing site-specific ICFs, delegation log templates, and site-level SOPs from a protocol draft is time-consuming when done manually and carries a risk of internal inconsistency across documents.

How Kitsa Fits Into This Problem

Kitsa's KScribe platform is designed to reduce the regulatory document generation burden that falls on sites and study teams during startup. KScribe is built to assist with the drafting of trial-specific informed consent forms, site SOPs, and investigator-facing document summaries from source documents, so that the PI and coordinator can direct their time toward review, compliance verification, and participant-facing work rather than document assembly. For sites managing multiple concurrent protocols, Kitsa states that this shift in where effort is concentrated is operationally meaningful.

Key Takeaways

• The FDA defines PI qualifications broadly in 21 CFR 312.53, requiring demonstrated training and experience appropriate to the investigation, with the sponsor making the selection determination [2].
• GlobalData analysis, reported in sponsored content, shows that active clinical trial investigators declined by approximately 10% between 2017-18 and 2023-24, creating real demand for qualified new PIs [1].
• Sub-investigator experience is the most direct path to PI candidacy. Meaningful participation across the full study lifecycle, from startup through close-out, builds the practical foundation that sponsors evaluate during feasibility review.
• GCP training standards have been updated with ICH E6(R3), finalized in January 2025 and adopted by the FDA in September 2025. Training adequacy depends on institutional, sponsor, and jurisdictional requirements, not a universal FDA certificate [8].
• Signing FDA Form 1572 is a binding commitment to personal oversight of the trial; the investigator delivers this form to the sponsor, who retains it. Sub-investigators listed on the form are responsible for their delegated tasks, but overall site accountability remains with the signing PI [2] [15].
• Enrollment requires specific authorization conditions including IRB approval and a signed Form 1572, while other startup activities such as contracting, training, and system access can proceed in parallel.
• Sponsor relationships are built through execution quality. Clean data, on-time enrollment, and minimal protocol deviations on a first study determine whether additional protocols follow [13].

FAQ

Do I need to be a physician to become a principal investigator in a clinical trial?+

Not necessarily. FDA regulations require that a PI be qualified by training and experience, but the agency delegates the definition of those qualifications to the study sponsor [2]. PhDs, PharmDs, and in some cases advanced practice providers can serve as PIs depending on the study type, therapeutic area, and sponsor's determination. When a non-physician serves as PI, sponsors commonly require that a licensed physician be available to assess safety events requiring medical judgment. The specific arrangement is defined by the sponsor and documented in the study agreement.

What is FDA Form 1572 and what happens after a PI signs it?+

FDA Form 1572, the Statement of Investigator, is the document by which a clinical investigator formally commits to conducting a drug or biologic trial in accordance with the protocol, GCP standards, and all applicable federal regulations [2]. The investigator signs the form and submits it to the sponsor, not to the FDA. The sponsor retains it as a required study record. In common practice, sponsors include Form 1572 information in IND submissions to satisfy related reporting requirements, but investigators should not send the form directly to FDA [15]. By signing, the PI accepts personal responsibility for participant protection, informed consent, adverse event reporting, data integrity, and site oversight.

How long does it take to get IRB approval before a trial can start?+

IRB review timelines vary materially by institution and review type. PIs should build time for this review into startup planning from the moment a feasibility questionnaire is submitted, because enrollment cannot begin until approval is in hand.

What is the difference between a principal investigator and a sub-investigator?+

The PI holds overall responsibility for the conduct of the trial at the site, including supervision of all study team members. Sub-investigators are individuals designated by the PI to perform specific study procedures or make defined study-related decisions, and they are listed on FDA Form 1572 for drug trials under 21 CFR 312.53(c)(1)(viii) [2]. The PI may delegate study tasks to sub-investigators, but overall accountability for the investigation at the site remains with the signing investigator, as established by 21 CFR 312.60 [2].

What certifications are most useful for becoming a PI?+

ACRP's Certified Principal Investigator (CPI) credential is the most directly relevant certification for aspiring PIs; it requires 3,000 hours of verifiable work experience, a doctorate-level degree (or qualifying advanced practice provider or sub-I designation), documented employment as a PI or sub-investigator for at least two of the most recent five years, and a two-year renewal cycle requiring 24 continuing education points [10]. SOCRA's CCRP certification is a cross-functional credential recognized across investigator, coordinator, and monitor roles, requiring two years of full-time or equivalent part-time experience and a three-year renewal cycle requiring 45 continuing education hours [11]. GCP training through the CITI Program is a baseline expectation at many research institutions; investigators should confirm whether their institution or sponsor requires E6(R3)-aligned training, given the guidance was adopted in 2025 [8].

What do sponsors look at when selecting a PI for the first time?+

Sponsors evaluate PI qualifications, therapeutic area expertise, patient population access, site infrastructure, and performance history. For a first-time PI without prior trial performance data, the assessment focuses on clinical credentials, documented site systems, and realistic enrollment projections. Sites that can demonstrate trained staff, functioning SOPs, an active IRB relationship, and a defined patient access strategy are more likely to clear feasibility review than sites that list qualifications without operational evidence [13] [18].

References

1. [1] Clinical Trials Arena. "The Unsustainability of Clinical Trials and Need for Change." July 2025. (Note: sponsored content citing proprietary GlobalData analysis.) https://www.clinicaltrialsarena.com/sponsored/the-unsustainability-of-clinical-trials-and-need-for-transformative-change/
2. [2] eCFR. 21 CFR Part 312: Investigational New Drug Application. Subpart D: Responsibilities of Sponsors and Investigators. U.S. Government Publishing Office. https://www.ecfr.gov/current/title-21/chapter-I/subchapter-D/part-312/subpart-D
3. [3] eCFR. 21 CFR 312.68: Inspection of Investigator's Records and Reports. U.S. Government Publishing Office. (Establishes FDA's authority to access and copy investigator records; inspection conduct is governed by FDA's Bioresearch Monitoring Program.) https://www.ecfr.gov/current/title-21/chapter-I/subchapter-D/part-312/section-312.68
4. [4] Ochsner Journal. "Investigator Responsibilities in Clinical Research." Ochsner Journal, 2020;20(1):44-48. https://www.ochsnerjournal.org/content/20/1/44
5. [5] JAAPA. "PAs as Principal Investigators of FDA-Regulated Clinical Trials." Journal of the American Academy of Physician Associates, June 2023;36(6). https://journals.lww.com/jaapa/fulltext/2023/06000/pas_as_principal_investigators_of_fda_regulated.8.aspx
6. [6] ICH. E6(R3) Guideline for Good Clinical Practice, Section 1.34 (Sub-investigator definition). International Council for Harmonisation, January 2025. (21 CFR 312.3(b) independently defines a subinvestigator as any other member of the investigator's team.) https://database.ich.org/sites/default/files/ICH_E6%28R3%29_Step4_FinalGuideline_2025_0106.pdf
7. [7] ACRP. "The Clinical Research Investigator: Clarifying the Misconceptions." Association of Clinical Research Professionals, February 2022. https://acrpnet.org/2022/02/15/the-clinical-research-investigator-clarifying-the-misconceptions
8. [8] Federal Register. "E6(R3) Good Clinical Practice; International Council for Harmonisation; Guidance for Industry; Availability." FDA, September 9, 2025. FR Doc. 2025-17311. https://www.federalregister.gov/documents/2025/09/09/2025-17311/e6r3-good-clinical-practice-international-council-for-harmonisation-guidance-for-industry
9. [9] EMA. "Good Clinical Practice Inspectors Working Group." European Medicines Agency. Confirms ICH E6(R3) has been effective in the EU since 23 July 2025. https://www.ema.europa.eu/en/human-regulatory-overview/research-development/compliance-research-development/good-clinical-practice/good-clinical-practice-inspectors-working-group
10. [10] ACRP. "Certified Principal Investigator (CPI) Certification." Association of Clinical Research Professionals. https://acrpnet.org/certification/pi-certification
11. [11] SOCRA. "CCRP Certification: Quick Facts and Recertification Requirements." Society of Clinical Research Associates. https://www.socra.org/certification/certification-program/ccrp-certification-quick-facts/
12. [12] ACRP. "Functional Competency Guidelines for Principal and Sub-Investigators." Association of Clinical Research Professionals. https://acrpnet.org/acrp-partners-advancing-the-clinical-research-workforce/functional-competency-guidelines-for-principal-and-sub-investigators
13. [13] Sramek JJ, Carrillo MS, Cutler NR. "Establishing a Clinical Trial Site: A Primer for Aspiring Principal Investigators." Contemporary Clinical Trials Communications. October 2025;48:101561. PMID: 41142039. https://pmc.ncbi.nlm.nih.gov/articles/PMC12553015/
14. [14] IntuitionLabs. "Clinical Trial Start-Up Costs: A Breakdown and Benchmarks." April 2026. (Secondary commercial compilation; specific figures vary by site type, infrastructure baseline, and therapeutic area.) https://intuitionlabs.ai/articles/clinical-trial-start-up-costs
15. [15] eCFR. 21 CFR 312.53: Selecting Investigators and Monitors; 21 CFR 312.57: Record Retention by Sponsor. https://www.ecfr.gov/current/title-21/chapter-I/subchapter-D/part-312/section-312.53
16. [16] eCFR. 21 CFR Part 50: Protection of Human Subjects; 21 CFR Part 54: Financial Disclosure by Clinical Investigators; 21 CFR Part 56: Institutional Review Boards. https://www.ecfr.gov/current/title-21/chapter-I/subchapter-A/part-50
17. [17] Applied Clinical Trials. "A Closer Look at the 1572: Interpreting the FDA's Statement of Investigator Form." Applied Clinical Trials Online. https://www.appliedclinicaltrialsonline.com/view/closer-look-1572-interpreting-fdas-statement-investigator-form
18. [18] WCG / CenterWatch. "Clinical Trial Trends and Insights for 2025: 2024 Clinical Research Site Challenges Report." January 2025. https://www.wcgclinical.com/insights/clinical-trial-trends-insights-2025/

Suggested internal links: KScribe: AI Regulatory Document Generation | ICH E6(R3): What Sites and Investigators Need to Know | Informed Consent Form Templates | What Is an Investigator Brochure