Relationship Between QTPP and CQA

Introduction

In QbD) the development of a pharmaceutical product starts with understanding the patient and therapeutic needs. These needs are translated into a QTPP which serves as the blueprint for product development. From this blueprint, we identify the (CQAs), which are the measurable parameters that directly affect product quality, safety, and efficacy.

What is QTPP?

The QTTP is a prospective summary of the key quality characteristics that a drug product should ideally possess. It is established at the beginning of development and provides a clear vision of the final product.

Elements of QTPP include:

Dosage form and route of administration
Dosage strength
Intended use (therapeutic indication)
Pharmacokinetic characteristics (Cmax, Tmax, AUC)
Drug release profile (immediate or modified release)
Stability requirements (shelf life, storage conditions)
Quality standards (compendial requirements, regulatory expectations)

What are CQAs?

CQAs are the physical, chemical, biological, or microbiological properties of a drug substance, excipient, intermediate, or finished product that must be controlled within predefined limits.

Examples of CQAs:

Assay (potency)
Dissolution rate
Degradation products/impurities
Sterility (for injectables)
Viscosity (for suspensions/syrups)
Particle size distribution (for inhalation or poorly soluble drugs)

Purpose: CQAs provide measurable checkpoints to ensure that the product meets the QTPP.

Relationship Between QTPP and CQA

The QTPP defines the “goal”: what the product should ideally achieve for patients.
The CQAs define the “path”: what parameters must be controlled to ensure the product reaches that goal.

In other words:

QTPP → product-level vision (patient-centric).
CQA → attribute-level control (scientist-centric).

The development process flows as:

Therapeutic Need → QTPP → Identify CQAs → Define CPPs/CMAs → Design Space → Control Strategy.

Example: Injectable Product (IV Solution)

QTPP (Injectable IV Solution):

Route: Intravenous injection
Dosage form: Sterile solution, 100 mg/5 mL vial
Strength: 20 mg/mL
Stability: 24 months at 25°C
Performance: Complete bioavailability, rapid onset
Quality: Meets pharmacopeial standards (USP, BP)

Derived CQAs:

Assay: 95–105% of label claim
pH: 4.5–5.5 (for stability and compatibility)
Particulate matter: Within USP <788> limits
Sterility: Must be sterile (no microbial growth)
Endotoxin levels: Within pharmacopeial limits
Degradation products: Below ICH thresholds

Conclusion

The QTPP is the foundation, describing the desired quality profile of the final drug product. From this foundation, the CQAs are identified as critical checkpoints that must be controlled to ensure the product meets its intended performance. Together, QTPP and CQA create a direct link between patient needs and scientific control, which is the essence of the QbD approach.

Related Topics: