Guideline for registering generic veterinary chemical products

1. Introduction

This document provides guidance for applicants proposing to register generic veterinary chemical products, including recommendations for when bioequivalence data should be submitted. The guidance may also be relevant for applications to change the formulation of an existing registered product where it is relevant to demonstrate equivalence between the approved and new formulation.

General guidance on generating efficacy and target animal safety data, particularly for veterinary chemical products containing new active constituents, is described in detail in the efficacy and target animal safety general guideline (Part 8). However, for applications involving generic products that contain existing active constituents, demonstration of equivalence with a registered reference product may be an appropriate way to satisfy the APVMA of the safety and efficacy criteria.

You should note that this guidance is only relevant to pharmaceutical type products. It is not relevant to immunobiological products, peptide products, DNA constructs and other products using biological delivery systems. For guidance on data submission for these types of products, you should refer to the data guidelines homepage.

In determining whether a proposed product is equivalent to a registered reference product, we will generally consider whether:

  • the proposed product and reference product have the same use pattern; and
  • the proposed product and reference product are pharmaceutically and/or biologically equivalent; and
  • whether the proposed product complies with applicable quality standards.

These considerations are discussed in more detail below.

Note that, as a general rule, the APVMA cannot use confidential commercial information relating to a nominated reference product if the use of the information would result in its disclosure. More information about use/disclosure of CCI can be found in the document 'Approach to managing confidential commercial information'.

1.1. Use pattern

For products to have the same use pattern as a registered reference product, the target animal species, dose rates, routes of administration, label claims and label instructions including withholding periods must all be the same.

1.2. Quality standards

Quality standards the APVMA will consider include:

  • compliance with appropriate standards for identity, potency, purity and stability; and
  • nomination of appropriately licensed site/s of product manufacture

1.3. Pharmaceutical Equivalence

To establish pharmaceutical equivalence between a proposed product and a registered reference product, we consider certain criteria which are consistent with the legislative definition of 'closely similar' as included in Regulation 1.2 in Schedule 6 to the Agvet Code Regulations. These criteria relate to the active constituent, the non-active constituents, the specifications and physico-chemical properties, the dose form and formulation types, and the use pattern of the product. You should note that all criteria are relevant in the assessment of pharmaceutical equivalence. The criteria for pharmaceutical equivalence are discussed individually below, but are all considered together when determining pharmaceutical equivalence.

1.3.1. Active Constituent

In relation to the active constituent, the proposed and reference chemical products are considered to be closely similar (pharmaceutically equivalent) if:

  • the active constituent(s) in the proposed chemical product is the same as the approved active constituent(s) in the reference chemical product; and
  • the concentration of the active constituents are the same

When reviewing active constituents against these criteria, we check whether the standard of the active constituents are compendial (for example European Pharmacopoiea (EP) or British Pharmacopoiea (BP)) or manufacturer's specification (MS). We review and compare the concentrations and active constituent specifications (including identity, purity, potency, and heavy metals) of the proposed and reference products and make a determination as to whether they can be considered the same.

1.3.2. Non-active constituents

In relation to the non-active constituents, the proposed and reference chemical products are considered to be closely similar (pharmaceutically equivalent) if either:

  • the non–active constituents in the formulations of the proposed and reference chemical products are the same, or are equivalent substances, at the same or equivalent concentrations; or
  • if the non–active constituents in the formulations of the proposed and reference chemical products are neither the same nor equivalent, the differences in the formulations are minor and are not expected to have adverse implications on product quality or biological activity in terms of efficacy, safety or residues

When reviewing non-active constituents against these criteria, we check whether the standard of the active constituents are compendial (for example European Pharmacopoeia (EP) or British Pharmacopoeia (BP)) or manufacturer's specification (MS). We review and compare the non-active constituents with regard to their concentration and purpose in the formulation, and make a determination as to whether they can be considered the same or equivalent substances. If they are neither the same nor equivalent, we make a determination as to whether the differences are expected to have adverse implications on product quality or biological activity in terms of efficacy, safety or residues.

1.3.3. Specifications and physico-chemical properties

In relation to the specifications and physico-chemical properties, the proposed and reference chemical products are considered to be closely similar (pharmaceutically equivalent) if either:

  • the proposed and reference chemical products specifications (including release and expiry limits and test methods) and physico-chemical properties (including pH, particle size, crystal form and, where applicable, dissolution profile, payout rate and payout period) are the same or equivalent; or
  • if the specifications and physico-chemical properties of the proposed and reference chemical products are neither the same nor equivalent, the differences in the specifications and properties are minor and are not expected to have adverse implications for product quality or biological activity in terms of efficacy, safety or residues

When reviewing specifications and physico-chemical properties against these criteria, we review and compare the product specifications and other physico-chemical properties of the products and make a determination as to whether they can be considered the same or equivalent. If they are neither the same nor equivalent, we make a determination as to whether the differences are expected to have adverse implications on product quality or biological activity in terms of efficacy, safety or residues.

1.3.4. Dose form and formulation type

In relation to the dose form and formulation type, the proposed and reference chemical products are considered to be closely similar (pharmaceutically equivalent) if:

  • the dose form and formulation type of the proposed and reference chemical products are the same

When reviewing dose form (for example, a product that is administered by injection) and formulation type (for example, an aqueous solution) against this criterion, we review and compare the dose form and formulation type and make a determination as to whether they are the same.

1.3.5. Use pattern

In relation to the use pattern, the proposed and reference chemical products are considered to be closely similar (pharmaceutically equivalent) if:

  • the use patterns (including target animal species, dose rates, routes of administration and withholding periods) and instructions on the labels of the proposed and reference chemical products are the same; and either:
    • the claims on the labels of the proposed and reference chemical products are the same; or
    • if the claims are different, the claims on the label of the proposed chemical product are fewer or reduced compared to the claims on the approved label of the reference chemical product.

When reviewing the use pattern against these criteria, we review and compare the proposed label wording of the new product and the approved label wording of the reference product and make a determination as to whether they are the same. We also determine whether the claims on the proposed label and fewer or reduced compared to the reference product label.

1.3.6. Biological equivalence

For products to be considered biologically equivalent to a registered reference product, they must have the same biological activity such as efficacy, safety or residues.

Biological equivalence is typically demonstrated by the conduct of bioequivalence studies—that is—the rate and extent of absorption of the therapeutic moiety should not be significantly different when administered at the same molar dose under similar conditions.

Where two or more products exhibit comparable rates and extent of absorption of the active constituent (bioavailability) they may be regarded as biologically equivalent. Bioequivalence studies can be used to demonstrate claims that a new product will have the same target species efficacy as a registered reference product. Establishment of comparable bioavailability with a reference product may obviate the need for conduct of clinical trials to provide data on target animal efficacy and safety.

Bioequivalence cannot necessarily be extrapolated to animal safety; however applicants can augment their bioequivalence studies with information about the safety of the excipients used in their proposed product. This may come from publically available information including MSDS and reference texts on excipients and their levels commonly used in the preparation of medicines. Further, applicants may refer to their own registered products in demonstrating that an excipient is safe for the proposed purpose at the proposed concentration.

We note that other considerations such as palatability, tissue irritancy, and in the case of the target animal being a food-producing animal, the level of residues in commodities for human consumption are not covered by bioequivalence data. Applicants should refer to the relevant data guidelines on the APVMA website as these considerations are outside the scope of this guideline.

2. Bioequivalence studies

Bioequivalence studies (ie blood concentration, pharmacological end-point, and clinical end-point studies) should be conducted in accordance with good laboratory practice and good clinical practice.

Bioequivalence studies are often used when an applicant applies for registration of a generic version of a registered veterinary chemical product. They may also be used to demonstrate efficacy in a variety of other situations, including:

  • as part of an application for registration of multiple products that contain the same new active constituent in different dose forms
  • to support registration of a product which has an alternative dosage form or new route of administration
  • to support approval of a formulation or manufacturing change which may affect product bioavailability
  • to support correlation between development stage formulations and final formulation
  • to support correlation between overseas formulation, reference product formulation and proposed generic product formulation

It is important to note that bioequivalence studies in food-producing animals are unlikely to be supportive in lieu of residues data.

Bioequivalence studies can demonstrate comparable animal safety with a reference product only in terms of the active constituent. Differences in the excipients in product formulations and different product specifications may result in tissue irritancy and other adverse effects. Animal safety aspects of a generic product formulation should therefore be addressed by animal safety studies and/or provision of relevant scientific argument.

The systemic bioavailability approach cannot be applied to veterinary products which are not intended to be delivered into the animal's general circulation. Alternative methods may be appropriate in these cases, such as studies using pharmacodynamic end-points. Blood concentration (pharmacokinetic) studies may not be relevant for active constituents which are active in the organ or tissue where the product is administered (for example the skin and gut) and which may also be absorbed and act systemically. Examples include topical ectoparasiticides and some oral anthelmintics. Clinical end-point studies such as comparative field trials are more relevant in these situations.

Applicants should refer to the VICH guideline on bioequivalence, or the FDA or EMA bioequivalence guidelines for guidance on the design and analysis of in vivo bioequivalence studies.

3. Selection of a reference product for bioequivalence studies

When conducting bioequivalence studies, the proposed product should be tested against the original APVMA registered pioneer product. The reason for this is that the pioneer product would have undergone a complete evaluation against all of the statutory criteria. If the original pioneer product is not available, then the first approved generic product should be used.

4. Formulation-dependent dosage forms

Due to the nature of certain dosage forms, the APVMA considers that bioequivalence data may not be relevant for products that meet particular criteria. Conversely, due to the unique and peculiar properties of other dosage forms, we strongly recommend that bioequivalence data is provided. To assist you in making an application for a generic product, we have classified various product dosage forms to be either highly, moderately or minimally formulation-dependent. These classifications are discussed individually below. Where guidance is not available for a particular dosage form (for example, trans-dermal products), you should apply to us for pre-application assistance or a technical assessment.

4.1. Highly formulation-dependent dosage forms

For these product types the formulation, specifications, and physico-chemical properties of a proposed generic and pioneer reference product should be identical in order to be considered equivalent. Minor differences in the formulation of such products may significantly affect the bioavailability and pharmacokinetics of the active constituent.

In vivo data to support equivalent biological activity such as efficacy, animal safety, and for food-producing species - residues data, is almost always relevant for these types of products. Animal safety data should address aspects associated with the formulation such as tissue irritation and adverse effects.

The following types of products fit the criteria for highly formulation-dependent dosage forms:

  • Suspensions
  • Intramammary infusions
  • Pour-on formulations and other topical applications with a systemic action
  • Implants for subcutaneous and/or intramuscular insertion.
  • Any products delivered by devices or modified-release dose forms, including intrarumenal devices and gastro-resistant capsules (but not ordinary gelatin capsules)
  • Any product with a narrow therapeutic range*

*Veterinary chemical products with a narrow therapeutic range or narrow tolerance range (margin of safety) contain active constituents where blood concentrations are critical for efficacy or animal safety, and/or which require monitoring of therapeutic concentrations or pharmacodynamics, and/or the product label indicates a narrow therapeutic range. Examples include digoxin, phenytoin, primidone, theophylline, and warfarin. If any product with a narrow therapeutic range is not identical to the reference product, comparable efficacy and animal safety should be demonstrated by the submission of in vivo studies (for example clinical efficacy trials and/or bioequivalence studies).

4.2. Moderately formulation-dependent dosage forms

For these product types, the formulation, specifications, and physico-chemical properties of the generic and pioneer reference product should not be significantly different in order for the generic product to be considered equivalent.

However, when satisfactory in vitro pharmaceutical data, together with valid scientific argument as to why this should be acceptable as proof of biological equivalence, is provided - in vivo data supporting equivalent biological activity will generally not be applicable for these types of products. The applicant should also satisfactorily address any potential for tissue irritation or adverse effects. The provision of in vitro comparative pharmaceutical data and relevant scientific argument/data in lieu of bioequivalence data will be considered on its merits once the application has been made.

The following types of products fit the criteria for moderately formulation-dependent dosage forms:

4.2.1. Tablets and non-aqueous solutions (including pastes) for oral administration

In vivo bioequivalence studies may not be applicable for some moderately formulation-dependent dose forms. For example, for certain oral immediate-release dose forms (for example, tablets) containing certain active constituents with a systemic action, provided that in vitro dissolution data correlates with in vivo bioavailability, it can be used as a surrogate for in vivo bioequivalence. This is commonly referred to as in vitro–in vivo correlation. Comparable efficacy may therefore be demonstrated for these products by using in vitro dissolution data together with other relevant scientific data or argument.

Bioequivalence studies may not be applicable for oral immediate-release dose forms if the generic product is pharmaceutically equivalent to the reference product. Proof of pharmaceutical equivalence should include data on solubility and permeability for the active constituent and equivalent dissolution rate for the formulated product.

Bioequivalence studies may not be applicable for non-aqueous solutions and pastes that are not suspensions. This is conditional that a suitable validated dissolution test that can differentiate between batches with acceptable and non-acceptable performance of the product in vivo, together with valid scientific argument, is provided.

Applications to register generic products that have modified-release formulations should always be accompanied by bioequivalence studies.

4.2.2. Simple aqueous solutions for subcutaneous and/or intramuscular injection

Bioequivalence studies may not be applicable for aqueous solutions intended for injection by subcutaneous and/or intramuscular routes if the generic product is pharmaceutically equivalent to the reference product. The pH and specific gravity specifications of the generic product should be the same as, or within the range of, the specifications of the reference product. You could also provide information, such as published articles, that indicate that the pH of the proposed product is suitable. Injection dose volumes should also be the same.

4.2.3. Teat dips and sprays

Efficacy Blood level bioequivalence studies are not relevant for teat dip and spray products. For applications to register new generic teat dip and spray products it is not necessary to provide in vivo clinical efficacy studies. In vitro antibacterial studies (AOAC 960.09 or BS EN 1656:2009 are recommended) should be provided for these applications and for applications to vary the formulation of registered teat dip and spray products.

For iodine-based products, the in vitro free iodine content and the pH of the diluted product should also be provided, along with justification/published information supporting known efficacious levels of these measurements. In vitro antibacterial studies may not be necessary for variation applications (eg certain simple formulation changes) if the product specifications are unchanged. For variation applications where the product specifications are changed in vitro antibacterial studies should be provided.

Safety The potential for the product to cause tissue irritation should be considered for applications to register new generic teat dip and spray products and for applications to vary the formulation of registered teat dip and spray products. Accordingly, in vivo clinical studies or valid scientific argument demonstrating the non-irritancy of the product to the target animal should be provided. For example, this information might include addressing the pH of the product, publicly available information or history of use of an excipient in other APVMA registered products with the same use pattern.

4.3. Minimally formulation-dependent dosage forms

The product types below are minimally formulation-dependent dosage forms in which differences in the formulations, specifications, and physico-chemical properties of the proposed generic and pioneer reference product are less likely to have a significant effect on the bioavailability and pharmacokinetics of the active constituents.

Provided they are not expected to have adverse implications for product quality, or other aspects such as efficacy, safety or residues, bioequivalence data will not usually be applicable for these types of products. The provision of relevant scientific argument in lieu of bioequivalence data will be considered on its merits once the application has been made.

Generally, products that fit these criteria will be stable in the gastrointestinal tract and have high solubility and high permeability. Other factors we will consider when evaluating an application for a generic product include:

  • the risk of therapeutic failure or adverse reaction
  • the risk of bioinequivalence
  • aqueous solubility
  • intestinal permeability
  • pharmacokinetic properties
  • rate of dissolution
  • effects of the excipients on the bioavailability of active constituent
  • effects of the excipients on target animal safety
  • particle size, polymorphism and manufacturing process

The following types of products fit the criteria for minimally formulation-dependent dosage forms:

4.3.1. All dose forms that are comprised of 100% active constituents

Bioequivalence studies are generally not applicable for generic products that consist entirely of the same active constituent, including inhalation anaesthetics.

4.3.2. Simple aqueous solutions for intravenous injection

Bioequivalence studies are generally not applicable if the generic product is intended to be administered by intravenous injection as an aqueous solution containing the same active constituent in the same concentration as the reference product. A simple aqueous solution is a solution that contains the active constituent(s), water and buffers, preservatives, colouring agents and no other types of constituents. A simple aqueous solution can be further defined as a homogenous mix in which the solute is in molecular dimensions. Simple aqueous solutions do not include emulsions or suspensions.

4.3.3. Simple aqueous solutions administered orally including water-soluble powders administered orally via drinking water

Bioequivalence studies are generally not applicable if the product is an aqueous oral solution at the time of administration and contains the same active constituent(s) in the same concentration(s) as an oral solution reference product. This is conditional that the excipients contained in it do not cause irritation to tissues and will not affect gastrointestinal transit, absorption, solubility or in vivo stability of the active constituent.

4.3.4. Simple aqueous solutions applied topically that act locally (not teat dips or sprays)

If the product is an aqueous topical solution at the time of administration and contains the same active constituent(s) in the same concentration(s) as a topical solution reference product, bioequivalence studies are generally not applicable. This is conditional that the excipients contained in it do not cause irritation to tissues and will not affect absorption or in vivo stability of the active constituent. Whenever systemic exposure resulting from locally applied, locally acting products entails a risk of systemic adverse reactions (for example, corticosteroids) or tissue residues, systemic exposure should be measured.

4.4. Conducting studies

4.4.1. Bioequivalence studies

Applicants conducting bioequivalence studies should refer to the following guidance documents for further information. While these documents may stipulate mandatory requirements, they have been written specifically by and for each regulatory agency and are not mandatory requirements for APVMA applications. You should refer to these documents for general guidance only.

Guidance for Industry: Bioequivalence: Blood Level Bioequivalence Study (VICH GL52)

Guideline on the conduct of bioequivalence studies for veterinary medicinal products (EMA)

Guidance for Industry: Bioequivalence guidance (FDA)

4.4.2. Dissolution studies

It is important to note that dissolution studies that are to be used as a surrogate for in vivo bioequivalence to satisfy target animal efficacy and safety criteria are not the same as the dissolution data provided as evidence of product quality to satisfy chemistry and manufacture safety criteria. Applicants should refer to the EMA guideline for conduct of bioequivalence studies to find the section about dissolution guidelines for more information. This guideline provides some detail of the dissolution equivalence data that could be considered in lieu of bioequivalence studies.

In evaluating dissolution data relevant to target animal efficacy and safety, consideration is to be given to the dissolution test method and the statistical analysis (such as the similarity factor) of the test results. The dissolution profiles should cover at least three time points, using three different buffers (pH 1 - 6.8). Buffers may be different from those that are recommended provided that valid scientific justification is provided by the applicant. Such justification may be related to:

  • the particular active constituent involved
  • the species the product is intended for
  • which portion of the gastrointestinal tract absorption takes place
  • whether environmental pH will affect the change from a pro-drug

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