Dr. Shawn R. Lockhart, PhD D(ABMM) Antifungal Susceptibility Testing committee’s perspective on the development and use of ECVs Dr. Shawn R. Lockhart, PhD D(ABMM) Mycotic Diseases Branch, Centers for Disease Control and Prevention CLSI, Spring 2018 1/27/2017

Objectives: The mindset of the antifungal susceptibility testing committee Data collection Data presentation Use

Some initial thoughts… ECVs could promote more susceptibility testing because they will allow MIC values to be put into context Right now, too many times we have to say “We can test that, but we won’t know what the numbers mean”

Why would we develop ECVS if nobody knows how to use them? How will anyone know how to use them if we don’t develop them?

Why not? Antifungal susceptibility testing is not routine, especially in the US Most of the data comes from just a few labs New antifungals are few and far between

Will they come?

Definition The minimal inhibitory concentration/minimal effective concentration value that separates fungal populations into those with and without acquired and/or mutational resistance based on their phenotypes (MICs)

CLSI Rules for establishing an ECV Only data generated using the protocol in CLSI document M27 can be used Species identification must be molecular or MALDI-TOF The iterative statistical method with a 97.5% cutoff is used for ECV determination

100, 3, 50% 100 isolates of a species must be tested The isolates have to come from at least 3 different labs No more than 50% of the data from a single lab

Differences between breakpoints and ECVs Require an MIC distribution, pharmakokinetic/pharmacodynamics data, and clinical treatment and outcome data Require an MIC distribution Can be used to predict clinical success Does not necessarily predict clinical success   Can be used to identify isolates that may harbor a mutation Extremely difficult to generate as treatment and outcome data are rare Can be generated against any species as long as enough isolates exist

Points of emphasis in the document ECVs do not allow us to determine whether a given bug/drug combination is likely to work only whether a particular MIC value is “normal” (wild type) or “not normal” (non-wild type) Treatment decisions will be based on “institutional knowledge”

When should an ECV not be used? When breakpoints have been published As a strong predictor of clinical response to therapy Rather as only an indicator of possibly acquired resistance mechanisms which could affect response to treatment

CLSI website data available Cryptococcus neoformans and fluconazole Fluconazole Lab 1 Lab 2 Lab 3 Lab 4 Lab 5 Lab 6 Total ≤0.125 4   0.25 9 1 2 12 0.5 31 7 40 60 28 30 3 127 190 96 376 176 106 111 5 39 19 456 8 27 26 16 11 89 6 20 32 10 64 >64 507 238 246 21 69 56 1137

Sample data set

Do ECVs identify non-wild type isolates? Number of isolates MIC in µg/ml 1,380 isolates

Do ECVs identify non-wild type isolates? FKS Mutation Number of isolates MIC in µg/ml

Do ECVs identify non-wild type isolates? TR34 Number of isolates MIC in µg/ml Jacques Meis, personal communication

Obstacles exist…not all data is useable MIC Value Lab 1 Lab 2 Lab 3 Lab 4 Composite 0.0005   1 0.001 0.002 0.004 0.008 2 0.016 12 0.03 13 14 0.06 3 7 0.125 10 9 23 0.25 6 20 39 0.5 8 22 4 Total 19 41 36 35  131

What else can we do?

Are ECVs going to be useful? Yes. We now have a pretty clear definition of what is phenotypic wild type Clear definition of what is not phenotypic wild type Dosage and duration can be based on whether an isolate looks like what we would consider “normal”

Suggested comment for discussion and for the report Provided wording… Isolate Antifungal Agent MIC ECV Suggested comment for discussion and for the report Cryptococcus neoformans fluconazole 32 g/mL 8 g/mL There are currently no BPs for C. neoformans and drug fluconazole. The fluconazole MIC is above the WT MIC which suggests that this isolate may have an acquired mechanism of resistance and should be considered NWT.   The clinical implication of finding a NWT MIC is currently unknown. If the agent in question is being used for treatment, the patient should undergo clinical review, and in consultation with an infectious disease physician/pharmacist, the decision should be made to (i) continue the agent at the current dose, (ii) increase the dose of the agent, or (iii) switch to an alternative agent.

Outreach Review article on Establishment of ECVs for antifungals Talks at major meetings ICAAC, ASM Microbe ISHAM

Extra thoughts… ECVs will only be established for species and antifungal combinations for which there is thought to be clinical efficacy For example, no ECVs for Cryptococcus and echincandins ECVs can be established for any species as long as there are enough isolates to test

Summary The Antifungal Subcommittee has begun developing ECVs for specific fungus/antifungal combinations We believe that ECVs will be clinically useful ECVs will rely on “institutional knowledge” of antifungal PK/PD

Thank you!