One of the emerging challenges of the IMpassion130 trial of the combination of nab-paclitaxel and atezolizumab versus nab-paclitaxel alone in triple negative breast cancer (TNBC) is that pathologists can’t reliably read PD-L1 on immune cells.

Georgia State Capitol in Atlanta

This issue came up in an insightful talk by David Rimm MD PhD (@RimmPathology), Professor, Departments of Pathology and Medicine (Oncology) at Yale in an education session at this year’s AACR annual meeting in Atlanta where he spoke about, “Predicting immunotherapy response with protein-based tools: PD-L1 and beyond.”

BSB readers will recall Dr Rimm was a hard hitting discussant of the CheckMate–227 trial data for the combination of nivolumab and ipilimumab in first-line non-small cell lung cancer (NSCLC) at AACR18. He correctly predicted that tumor mutational burden (TMB) as a biomarker would predict PFS but not overall survival, based on an analysis of their cohort at Yale. He turned out to be right!

The implication of this was that BMS subsequently withdrew their EU/US regulatory filings for CM227 in 1L NSCLC when the hazard ratios (HR) for high and low TMB turned out to be identical.

If you missed it, do listen to the episode 22 of the Novel Targets Podcast we produced from AACR18 (Link), where we took a closer look at TMB as a biomarker, and the phase 3 lung cancer clinical data presented at the meeting.

Will we see challenges emerge with the Ventana SP142 assay?  What about the implications for Merck’s KEYNOTE-355 trial in TNBC?

In this BSB post, we discuss these issues and explore many of the nuances that readers should be aware of in TNBC.

In addition to Dr Rimm’s candid and hard hitting interview, we also invited Professor Sherene Loi (@LoiSher) to review Dr Rimm’s commentary and offer a clinical perspective on the points he raised.

She’s a consultant medical oncologist at the Peter MacCullum Centre in Australia, where she holds the National Breast Cancer Foundation of Australia Endowed Chair and is head of the Translational Breast Cancer Genomics and Therapeutic Laboratory.

Professor Loi is also one of the authors of the paper published in The New England Journal of Medicine that reported the results of the IMPassion130 trial.

If you’d like to read Dr Rimm’s candid interview and Professor Loi’s clinical perspective, become a subscriber to BSB and support independent science journalism. As of today, 75% of our subscribers are repeat buyers – do consider joining them!

In the second part of the interview with Dr Rimm (to be published separately), we’ll hear about some of the new data his lab presented at AACR19 and where he sees the future for TMB and other immune biomarkers.

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