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# FDA Lifts Hold on Pieris Pharma Clinical Trial
- URL: https://www.fdaweb.com/fda-lifts-hold-on-pieris-pharma-clinical-trial/
- Published: 2021-01-19T12:00:00.000Z
- Updated: 2026-09-14T16:43:23.000Z
- Author: David McFarland
- Tags: Drugs, #legacy-id-D5148471

FDA has removed a partial clinical hold on a Pieris Pharmaceuticals Phase 1 study of PRS-343 that was issued while the company conducted an additional in-use and compatibility study requested by the agency. Currently-enrolled patients were permitted to continue to receive treatment, the company said, but no new patients could be enrolled until the hold was resolved. PRS-343 is currently being evaluated for treating HER2-positive solid tumors.  

The company [earlier said](https://www.fdaweb.com/pieris-pharma-study-of-cancer-drug-on-hold/) the partial hold followed discussions with FDA about the in-use study supporting the technical setup for clinical administration of PRS-343\. “Specifically,” it said, “FDA had requested that Pieris conduct an additional in-use and compatibility study of PRS-343 with various infusion materials under specific conditions to confirm suitability of PRS-343 for administration in clinical settings.”  
  
Pieris describes PRS-343 as a 4-1BB/HER2 fusion protein comprising a 4-1BB-targeting Anticalin protein and a HER2-targeting antibody. Ongoing Phase 1 studies of PRS-343 include a monotherapy study and a combination study with atezolizumab. Based on encouraging initial results from both studies, the company says it is actively working toward initiating a Phase 2 study in combination with ramucirumab and paclitaxel for treating HER2-positive gastric cancer in a second line setting shortly.