The International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH) just published the final version of the harmonized drug-drug interaction (DDI) guideline (ICH M12). The guideline is pending adoption by regional regulatory health agencies. ICH released a companion Q&A document in parallel to the guidance. ICH M12 recommends in vitro and in vivo DDI studies for new medicinal products.
The guideline is generally relevant to small molecule drug development. It also gives limited consideration to therapeutic proteins and antibody-drug conjugates (ADCs; read about the FDA ADC clin pharm guidance here).
The document isn’t as comprehensive as some regional guidelines which also consider food effects, DDIs with oral contraceptives, and absorption-related DDIs including pH-mediated ones. Thus, regional guideline(s) remain valid. Consult them for the more focused aforementioned topics. ICH made minimal changes to the draft version of ICH M12 (July 2022) during the revision process for the final guideline.
Time to review and update your DDI packages!
We recommend reviewing all available in vitro (and in vivo) DDI data with a fresh perspective.
-
- Do your in vitro studies fulfill the ICH M12 guideline requirements?
- After implementing the ICH M12 guideline, will a negative DDI risk remain so or be considered positive or inconclusive? Will your planned in vivo DDI study no longer be required as your assumed positive in vitro signal is now considered negative?
- Are the upcoming changes already factored into your program timelines? Could health authorities put your drug development program on clinical hold next year due to a lack of relevant in vitro data?
As an example, the guideline has less strict criteria (cutoffs, R-values) i.e. for when an in vitro signal is considered to be relevant in vivo, for a time-dependent-inhibitor (TDI) and more strict criteria when evaluating enzyme induction. Look closely at the ICH M12 DDI guideline to determine whether your in vitro data or planned studies will reach the desired standard.
Changes in the ICH guideline
The DDI guideline is very detailed. Hence, we have summarized the key changes below and in the table for quick reference.
Nomenclature: While the draft guidance used the terms “victim” and “perpetrator” drugs, the final document now refers to “object” (a substrate of an enzyme or transporter) and “precipitant” (a drug that can induce or inhibit an enzyme or a transporter). ICH added a glossary to the guidance’s appendix.
Protein Binding: A new section was added describing the suitability of a given methodology which allows using unbound human plasma fraction less than 0.01 (fu <0.01) for a DDI assessment using basic methods.
Biomarkers: In contrast to the draft version, ICH now presents a biomarker approach. The guidance mentioned plasma coproporphyrin I (hepatic OATP1B1/3), plasma and urine N-methylnicotinamide and N-methyladenosine (renal OCT2, MATE1, MATE2K), plasma pyridoxic acid (renal OAT1/3), and plasma 4β-hydroxycholesterol/cholesterol ratio and urine 6β-hydroxycortisol/cortisol ratio for CYP3A. This approach is very useful, and PBPK models can leverage it.
For more details, read our blog on using Coproporphyrin-1 (CP-1) as an endogenous biomarker for predicting OATP1B DDIs.
Table: Summary of key changes in ICH M12 guideline versus previous regional guidances
In vitro studies | |
Topic/Investigation | Final ICH M12 (differences from the draft version are in bold font) |
General Principles (Timing) |
|
Substrate of Metabolizing Enzymes |
|
CYP Reversible Inhibition |
|
CYP450 Time-dependent Inhibition (TDI) |
|
UGT Inhibition |
|
CYP Induction |
|
Mechanistic static model |
|
Substrate of Transporters |
|
Transporter Inhibition |
|
DDI of Metabolites |
|
Assay Conditions |
|
In vivo studies | |
General Principles (Timing) |
|
In vivo studies |
|
PBPK and population PK approaches |
|
Need help navigating the new requirements?
Our experts can help. Read our white paper to learn more about modeling and simulation approaches to predict DDIs.

The blog was first published on March 31, 2023. Eva Gil Berglund and Nathalie Rioux updated this blog in June 2024.