By Chris Wack 



  Vaccinex Inc. shares were up 18% to $6.25 after the company said it has entered into a clinical collaboration agreement with Merck & Co. to evaluate the combination of Vaccinex's investigational SEMA4D inhibitor, pepinemab, and Merck's anti-PD-1 therapy, Keytruda, in the treatment of patients with advanced, recurrent or metastatic head and neck squamous cell carcinoma. 


  The planned clinical collaboration with pepinemab and Keytruda (pembrolizumab) will consist of a dose escalation phase followed by an expansion phase that will enroll up to 65 HNSCC patients allocated to different levels of combined positive score of PD-L1 expression. 


  Combined positive score is a biomarker associated with benefit in response to immunotherapy, and a major goal of this study is to determine whether combination therapy can improve response in these populations. 


  Vaccinex said key endpoints of the study include objective response, progression free survival and overall survival. 


  Write to Chris Wack at chris.wack@wsj.com