Crossover design in confirmatory therapeutic trials

This week, FDA approved a new drug called Aqneursa (levacetylleucine) for the treatment of neurological symptoms associated with Niemann-Pick disease type C (NPC) - a rare disease - in adults and pediatric patients. FDA approval was based on the confirmatory phase 3 study using a crossover design. "The safety and efficacy of Aqneursa for the treatment of NPC were evaluated in a randomized, double-blind, placebo-controlled, two-period, 24-week crossover study. The duration was 12 weeks for each treatment period. The study enrolled 60 patients." The study design was discussed in the paper by Fields et al "N-acetyl-L-leucine for Niemann-Pick type C: a multinational double-blind randomized placebo-controlled crossover study" and the crossover study design was depicted as below. Patients were assessed during a baseline period and then randomized (1:1) to one of two treatment sequences: IB1001 (levacetylleucine) followed by placebo or placebo followed by IB1001 (levacetylleucine). Each sequence consists of a 12-week treatment period. The primary efficacy endpoint is based on the Scale for the Assessment and Rating of Ataxia

The advantages of the crossover design includes:

• It allows a within-patient comparison between treatments. Each patient serves as his/her own control
• Treatment contrasts estimated as a within subject effect
• Fewer subjects (smaller sample size) required for the study

The disadvantages of the crossover design includes: 

• Carryover effect of previous treatment to the next treatment
• Time dependent changes
• Increased time length of the trial
• Drop out issue, too many visits
• May require complicated statistical modeling - for example, mixed model to analyze the data

The crossover design is very common and almost the default design for bioequivalence studies. As stated in FDA's guidance for industry "Bioequivalence Studies With Pharmacokinetic Endpoints for Drugs Submitted Under an ANDA", crossover design was recommended in most of situations. 

"For most dosage forms that release a drug intended to be systemically available, FDA recommends that applicants perform a two-period, two-sequence, two-treatment, single-dose,crossover study using either healthy subjects or other populations, as appropriate. In this design, each subject should receive each treatment (the test and the reference product) in a random order. 

A replicate crossover study design (either partial or fully replicate) is appropriate for drugs  whether the reference product is a highly variable drug or not. A replicate design can have the advantage of using fewer subjects compared to a non-replicate design, although each subject in a replicate design study would receive more treatments."

However, crossover designs are seldom employed in confirmatory therapeutic clinical trials, which typically use clinical endpoints rather than pharmacokinetic ones. The most common design for these trials is the traditional randomized controlled trial (RCT) with parallel groups, where patients are randomly assigned to either an experimental treatment group or a placebo.

In some special situations such as the rare disease drug development, the crossover design may be employed in the phase 3 confirmatory clinical trials. Here are some examples: 

• Samsung Bioepis Co. "A Study to Compare SB12 (Proposed Eculizumab Biosimilar) to Soliris in Subjects With Paroxysmal Nocturnal Haemoglobinuria" - the product" - FDA approved the product based on this study with crossover design
• KalVista Pharmaceuticals "A Phase III, Crossover Trial Evaluating the Efficacy and Safety of KVD900 for On-Demand Treatment of Angioedema Attacks in Adolescent and Adult Patients With Hereditary Angioedema (HAE)" - NDA based on this study is under FDA's review
• GSK "Cross-Over Study in Subjects With COPD, Evaluating Lung Function Response After Treatment With Once Daily Umeclidinium 62.5mcg, Vilanterol 25mcg, and Umeclidinium/​Vilanterol 62.5/​25mcg"
• Wiley et al (2016) "A Crossover Design for Comparative Efficacy: A 36-Week Randomized Trial of Bevacizumab and Ranibizumab for Diabetic Macular Edema"
• Bethoux et al (2024) "A randomized, double-blind, placebo-controlled trial to evaluate the effect of nabiximols oromucosal spray on clinical measures of spasticity in patients with multiple sclerosis"  
• Watz et al (2016) Effects of indacaterol/glycopyrronium (QVA149) on lung hyperinflation and physical activity in patients with moderate to severe COPD: a randomised, placebo-controlled, crossover study (The MOVE Study)
• Zhang et al (2022) Design and analysis of crossover trials for investigating high-risk medical devices: A review

ICH E9 "STATISTICAL PRINCIPLES FOR CLINICAL TRIALS" have a section discussing crossover design:

FDA's Good Review Practice: Clinical Review of Investigational New Drug Applications" also discussed the advantages and disadvantages of the crossover design:

In confirmatory therapeutic trials using a crossover design, an additional concern is the potential for unblinding. As the same patient receives both the experimental drug and the placebo, the patient might be able to identify or guesstimate the treatment group they are assigned to based on slight differences in taste, smell, or side effects.

The Role of Radiolabeling in Clinical Studies: Exploring Lung Deposition and Mass Balance Studies

Radiolabeling is an advanced and valuable technique in clinical research that enables scientists to trace the journey of drugs through the human body. By attaching a radioactive isotope to a drug molecule (usually a small molecule), researchers can track its absorption, distribution, metabolism, and excretion (ADME). This technique provides precise, real-time data and is especially useful for two types of clinical studies: lung deposition studies and mass balance studies.

What Are Lung Deposition Studies?

Inhaled medications are commonly used to treat respiratory diseases like asthma, chronic obstructive pulmonary disease (COPD), alpha-1 antitrypsin deficiency, and cystic fibrosis. However, the efficacy of these treatments largely depends on how much of the drug reaches the target area in the lungs.

Lung deposition studies assess the distribution of inhaled drugs within the lungs. The primary goal of these studies is to ensure that the drug particles deposit in the right lung regions for optimal therapeutic effect. Radiolabeling plays a crucial role in these studies by enabling researchers to visualize and quantify how inhaled drugs spread through the respiratory system.

Radiolabeling in Lung Deposition Studies

Radiolabeling in lung deposition studies involves attaching a radioactive isotope, such as technetium-99m (99mTc), to the drug formulation. After inhalation, the radioactive emissions from the drug particles are detected using imaging techniques like gamma scintigraphy or positron emission tomography (PET). These images provide a detailed map of drug distribution within the lungs.

Key advantages of using radiolabels for lung deposition studies include:

• Accurate Measurement: Researchers can measure how much of the drug reaches the lungs and where exactly in the lungs it settles (central airways, peripheral airways, alveoli, etc.).
• Device Optimization: By studying how well different inhaler devices (e.g., dry powder inhalers, metered-dose inhalers, nebulizers) deliver the drug, researchers can refine device designs to improve drug delivery to the lungs.
• Personalized Treatment: Lung deposition patterns vary across individuals due to differences in lung anatomy, disease severity, and inhaler technique. Radiolabeling helps researchers tailor treatments to individual needs.

Imaging Techniques in Lung Deposition Studies

1. Gamma Scintigraphy: This is the most commonly used imaging method in lung deposition studies. It detects gamma radiation emitted from radiolabeled drug particles and generates detailed images showing how much of the drug is deposited in different parts of the lungs.

2. Positron Emission Tomography (PET): PET is a more advanced imaging technique that uses isotopes like carbon-11 to provide high-resolution, three-dimensional images of drug distribution in the lungs. While more expensive and complex than gamma scintigraphy, PET can offer more precise data on drug uptake and metabolism in the lungs.

Why Lung Deposition Studies Matter

• Efficacy: Lung deposition studies help determine if a drug reaches the specific areas of the lungs (for example, the peripheral part of the lung versus central part of the lung) where it's needed most. For example, drugs intended for deep lung penetration must reach the alveoli to be effective.
• Safety: By ensuring that a drug is delivered directly to the lungs and not to other parts of the body, these studies minimize systemic side effects.
• Regulatory Compliance: Regulatory agencies like the FDA and EMA often require data on drug deposition patterns to ensure safety and efficacy, especially for inhaled drugs.

Some Examples of the Lung Deposition Studies: 

• Brand et al (2009) Lung deposition of inhaled α1-proteinase inhibitor in cystic fibrosis and α1-antitrypsin deficiency ERJ
• Brank et al (2007) Lung Deposition of Radiolabeled Tiotropium in Healthy Subjects and Patients With Chronic Obstructive Pulmonary Disease  Journal of Clinical Pharmacology
• Van Holsbeke et al (2018) Use of functional respiratory imaging to characterize the effect of inhalation profile and particle size on lung deposition of inhaled corticosteroid/longacting beta2-agonists delivered via a pressurized metered-dose inhaler. Ther Adv Respir Dis 

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What Are Mass Balance Studies?

Mass balance studies, also known as absorption, distribution, metabolism, and excretion (ADME) studies, track the fate of a drug from administration to elimination. These studies are essential for understanding how much of the drug is absorbed into the bloodstream, how it is metabolized, and how it is excreted from the body.

Radiolabeling is critical in mass balance studies as it enables precise quantification of the drug and its metabolites in different biological samples, including blood, urine, feces, and sometimes breath.

Radiolabeling in Mass Balance Studies

In mass balance studies, radiolabeling involves attaching a radioisotope (such as carbon-14 or tritium) to the drug molecule. Once the drug is administered, researchers can track its movement through the body by measuring radioactive emissions in collected biological samples. The use of radiolabels allows for accurate and complete recovery of the drug and its metabolites, making it easier to determine:

• Total absorption: How much of the drug is absorbed into systemic circulation.
• Metabolic pathways: How the drug is broken down in the body and the metabolic products formed.
• Elimination: The routes through which the drug is excreted (e.g., urine, feces) and how much is removed from the body over time.

According to FDA guidance for industry (2024) "Clinical Pharmacology   Considerations for  Human Radiolabeled Mass Balance Studies", the following were stated:

A human radiolabeled (most commonly 14C or 3H) mass balance study is the single most direct method to obtain quantitative and comprehensive information on the absorption, distribution, metabolism, and excretion (ADME) of the drug in the human body.  

The mass balance study can provide information to: 

• Determine the overall pathways of metabolism and excretion of an investigational drug 
• Identify circulating metabolites 
• Determine the abundance of metabolites relative to the parent drug or total drug-related exposure 

The results from mass balance studies help to: 

• Provide information on which metabolites should be structurally characterized and which metabolites should undergo nonclinical safety assessment or drug-drug interaction (DDI) evaluation 
• Assess whether renal or hepatic impairment studies or certain DDI studies are recommended for the investigational drug 
• Assess the extent of absorption of the investigational drug 

Importance of Mass Balance Studies

1. Drug Safety: Mass balance studies help identify any potentially harmful metabolites that could lead to side effects. By understanding how a drug is metabolized, researchers can predict interactions with other medications.

2. Dose Optimization: These studies provide critical information for determining appropriate dosage levels by understanding how much of the drug remains in the system over time.

3. Regulatory Approval: Mass balance data is essential for regulatory submissions, providing authorities with a full picture of the drug’s pharmacokinetics and safety profile.

Challenges in Radiolabeled Mass Balance Studies

Although radiolabeling offers precise tracking of drugs, mass balance studies present a few challenges:

• Complexity: Preparing radiolabeled drugs requires specialized equipment and expertise, which can increase the cost and time required for studies.
• Radiation Safety: Even though radiolabels use minimal radiation doses, strict safety protocols must be followed to minimize exposure risks for study participants and researchers.
• Variability: Individual differences in metabolism can lead to variability in study results, requiring large sample sizes for accurate interpretation.

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Combining Lung Deposition and Mass Balance Studies

Radiolabeling enables researchers to link data from both lung deposition and mass balance studies. For inhaled drugs, this combined approach provides a complete picture of how the drug behaves after delivery: from deposition in the lungs to its absorption into the bloodstream and eventual elimination.

Conclusion

Radiolabeling plays a pivotal role in both lung deposition and mass balance studies, providing detailed, real-time insights into the distribution and metabolism of drugs within the body. These studies are indispensable for the development of safe and effective therapies, particularly for inhaled medications and other drugs that require precise delivery to target tissues.

By combining data from lung deposition studies with mass balance studies, researchers can optimize drug formulations, refine delivery devices, and ensure that new drugs meet regulatory requirements, all while enhancing patient outcomes.

Patents vs. Trade Secrets: Understanding the Best Approach for Your Innovation and Invention

In today’s competitive business landscape, protecting intellectual property (IP) is critical. Whether you’re an inventor developing a groundbreaking drug product or a company refining proprietary processes, understanding how to safeguard your creations is essential. Two key ways to protect intellectual property are patents and trade secrets. While both offer avenues to safeguard your innovations, they differ significantly in scope, cost, and long-term strategy. Here are the differences between patents and trade secrets.

What is a Patent?

A patent is a government-issued right that grants an inventor exclusive control over their invention for a limited time. It essentially provides a legal monopoly, preventing others from making, using, or selling the patented invention without permission.

Patents typically last 20 years (for utility patents) from the date of filing. During this time, the inventor has the right to license the invention, sell the patent rights, or enforce their exclusive ownership through legal channels. If clinical development takes a very long time, the remaining patent protection may be limited by the time the product is approved. After patents expire, the generic drugs may be brought to the market.

Key Features of Patents:

• Full Disclosure: When you file for a patent, you must disclose every detail about your invention to the public. This ensures that once the patent expires, others can build upon or use the invention.
• Protection Scope: Patents cover new and useful inventions, processes, or designs. Examples include novel machinery, medical devices, or software algorithms.
• Legal Enforceability: Patents can be enforced through lawsuits against infringers. If someone tries to use your invention without permission, you can seek legal redress.
• Costs: The costs associated with obtaining and maintaining a patent can be substantial, including filing fees, legal fees, and periodic maintenance fees over the life of the patent.

Example of a Patent: The iPhone, for example, is covered by thousands of patents, including both the hardware and software innovations.

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What is a Trade Secret?

A trade secret, on the other hand, is information that companies keep confidential to maintain a competitive advantage. Unlike patents, which require public disclosure, trade secrets thrive on secrecy. As long as the information remains secret and is valuable to the business, the protection can last indefinitely.

Unlike patents, trade secrets are not registered with any governmental agency. Instead, businesses take steps to keep the information secure—through non-disclosure agreements (NDAs), security protocols, and restricting access to the secret.

Key Features of Trade Secrets:

• Confidentiality: The defining characteristic of a trade secret is its secrecy. If the secret becomes public, the protection is lost.
• Indefinite Duration: As long as the secret is kept confidential, protection can last indefinitely. For example, the Coca-Cola formula has been protected for over a century.
• Lower Costs: Trade secrets don’t require the extensive costs associated with patents, though companies need to invest in maintaining secrecy, such as through legal contracts and security measures.
• Risk of Exposure: Trade secrets are vulnerable to accidental disclosure, reverse engineering, or independent discovery. If a competitor uncovers your secret by lawful means, you lose your exclusive advantage.

Example of a Trade Secret: The Coca-Cola formula is one of the most famous trade secrets, kept under tight security since the late 1800s. Also see Famous Trade Secrets in Business History and 5 Famous Trade Secrets People Use Everyday.

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Comparing Patents and Trade Secrets

	Patent	Trade Secret
Issued by	The United States Patent and Trademark Office (USPTO) – a government agency in the U.S. Department of Commerce Other corresponding agencies in other countries	None
Disclosure	Full public disclosure is required.	No disclosure; must remain confidential.
Duration	Limited to 20 years from the date of filing for utility patents.	Indefinite, as long as secrecy is maintained.
Cost	High, including filing and legal fees.	Low, mainly for maintaining security and contracts.
Protection Scope	Protects inventions, processes, or designs.	Protects confidential business information.
Enforcement	Legal enforcement through patent infringement lawsuits.	Legal action against theft or breach of contract.
Risk	After expiration, the invention enters public domain.	Vulnerable to exposure through reverse engineering or independent discovery.

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Choosing Between a Patent and a Trade Secret

When deciding between a patent and a trade secret, the nature of your invention, business strategy, and budget should guide your decision. Here are some questions to help you decide:

1. Do you want long-term protection?
• If your invention can be kept secret indefinitely and the risk of reverse engineering is low, a trade secret might be ideal. However, if public disclosure doesn’t harm your competitive advantage and your innovation is at risk of duplication, a patent offers legal protection for 20 years.
2. How costly is it to protect your innovation?
• Patents come with significant costs—filing fees, legal representation, and maintenance fees. For small businesses or startups, these costs can be prohibitive. In contrast, trade secrets require less upfront investment but need ongoing vigilance in maintaining confidentiality.
3. Will your innovation be reverse-engineered?
• If your innovation can easily be reverse-engineered or independently discovered (like a consumer product), a patent provides stronger protection. On the other hand, if your business relies on internal processes or formulas that competitors would struggle to uncover, a trade secret might be sufficient.
4. How much risk can you tolerate?
• Patents offer more certainty in protection, but once the patent expires, anyone can use the invention. Trade secrets are riskier, as they rely on maintaining secrecy, but they can offer indefinite protection as long as no one else uncovers the secret.

In the pharmaceutical and biotechnology industries, patents are the primary tool for safeguarding intellectual property. Trade secrets, on the other hand, can be challenging to maintain, especially with the frequent movement of scientists between companies.

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Conclusion

Both patents and trade secrets offer powerful tools for protecting your intellectual property, but each has its strengths and weaknesses. A patent is ideal when you want strong, enforceable protection and are willing to disclose your invention in exchange for a limited monopoly. Trade secrets, on the other hand, work best when you can keep an innovation confidential and want to avoid the high costs of patenting.

Ultimately, the choice between patents and trade secrets comes down to your specific needs, the nature of your innovation, and how you plan to leverage your competitive advantage in the marketplace. In many cases, businesses use both strategies (plus also the FDA exclusivity) to protect different aspects of their intellectual property, ensuring they maximize protection while minimizing risk.

Good Reading: 

• Nealey, Daignault, and Cai (2015) Trade Secrets in Life Science and Pharmaceutical Companies
• Trade secrets: a strategic element in the life sciences and biotechnology industries