Abstract 2214
Background
ENZA and APA are androgen receptor inhibitors approved for treatment of castration-resistant prostate cancer (CRPC) and nonmetastatic CRPC, respectively. Their chemical structures differ with ENZA having 2-cyanophenyl and dimethyl moieties and APA 2-cyanopyridyl and cyclobutyl moieties. In the SPARTAN clinical trial, APA treatment was reported to be associated with an increased incidence of skin rash compared with the placebo group, which was not observed with ENZA in the PROSPER trial in a similar patient population; therefore, we examined their in vitro chemical reactivity and hypersensitivity potential in an MDAM.
Methods
To assess possible reactivity of cyanopyridine, in vitro studies examining the chemical stability in buffer (+/- glutathione) and covalent binding to proteins (eg, bovine serum albumin [BSA]) were evaluated. For the MDAM, C57BL/6 mice were injected subcutaneously with APA, ENZA, or RD162 (Analogue 1), daily for 3 days at 25, 50, or 100 mg/kg/day. Brachial lymph nodes were harvested on day 6 and lymph node cellularity was analyzed by flow cytometry.
Results
The 2-cyanopyridine moiety of APA was found to be chemically reactive with the thiol nucleophile glutathione, resulting in rearranged thiazoline products. Radiolabeled APA, but not ENZA, was shown to react with mouse and human plasma proteins. Thiol nucleophiles decreased the extent of covalent binding to the model protein BSA while amine and alcohol nucleophiles had no effect, suggesting a reaction with cysteine sulfhydryl groups of proteins. In the MDAM, dose-dependent higher lymph node cellularity was observed for the APA groups (compared with the vehicle control), suggesting immune activation. ENZA and Analogue 1 demonstrated substantially less covalent binding activity and no change in lymph node cellularity (compared with vehicle) in the MDAM.
Conclusions
These data support the hypothesis that the 2-cyanopyridine moiety present in APA, but absent in ENZA or Analogue 1, may react with cysteine residues in proteins to form haptens that may trigger an immune response leading to the increased incidence of skin rash clinically observed in patients treated with APA, but not with ENZA.
Clinical trial identification
Editorial acknowledgement
Medical writing and editorial assistance funded by Pfizer Inc. was provided by Ira Mills, PhD, and Michele Salernitano from Ashfield Healthcare Communications.
Legal entity responsible for the study
Pfizer Inc. and Astellas Pharma, Inc.
Funding
Pfizer Inc. and Astellas Pharma, Inc.
Disclosure
M. Guha: Shareholder / Stockholder / Stock options, Employee: Pfizer Inc.. C. Ji: Shareholder / Stockholder / Stock options, Employee: Pfizer Inc.. X. Zhu: Shareholder / Stockholder / Stock options, Employee: Pfizer Inc.. J. Whritenour: Shareholder / Stockholder / Stock options, Employee: Pfizer Inc.. M. Hemkens: Shareholder / Stockholder / Stock options, Employee: Pfizer Inc.. S. Tse: Shareholder / Stockholder / Stock options, Employee: Pfizer Inc.. G.S. Walker: Shareholder / Stockholder / Stock options, Employee: Pfizer Inc.. E. Evans: Shareholder / Stockholder / Stock options, Employee: Pfizer Inc.. N.K. Khan: Shareholder / Stockholder / Stock options, Employee: Pfizer Inc.. M.B. Finkelstein: Shareholder / Stockholder / Stock options, Employee: Pfizer Inc.. E. Callegari: Shareholder / Stockholder / Stock options, Employee: Pfizer Inc.. R..S. Obach: Shareholder / Stockholder / Stock options, Employee: Pfizer Inc..
Resources from the same session
1242 - Monalizumab in combination with cetuximab in patients (pts) with recurrent or metastatic (R/M) head and neck cancer (SCCHN) previously treated or not with PD-(L)1 inhibitors (IO): 1-year survival data.
Presenter: Roger Cohen
Session: Poster Display session 3
Resources:
Abstract
4703 - Updated results of a phase II study evaluating accelerator-based boron neutron capture therapy (AB-BNCT) with borofalan(10B) (SPM-011) in recurrent squamous cell carcinoma (R-SCC-HN) and recurrent and locally advanced non-SCC (R/LA-nSCC-HN) of the head and neck
Presenter: Katsumi Hirose
Session: Poster Display session 3
Resources:
Abstract
3638 - Phase 3 KEYNOTE-048 Study of First-Line (1L) Pembrolizumab (P) for Recurrent/Metastatic (R/M) Head and Neck Squamous Cell Carcinoma (HNSCC): Asia vs Non-Asia Subgroup (subgrp) Analysis
Presenter: Makoto Tahara
Session: Poster Display session 3
Resources:
Abstract
2954 - Integrated data review evaluating safety, pharmacokinetics (PK) and immunogenicity of RM-1929 photoimmunotherapy (PIT) in subjects with locoregional, recurrent head and neck squamous cell carcinoma (rHNSCC).
Presenter: Jennifer Johnson
Session: Poster Display session 3
Resources:
Abstract
3629 - First line versus second line immunotherapy in recurrent/metastatic squamous cell carcinoma of the head and neck
Presenter: Caroline Even
Session: Poster Display session 3
Resources:
Abstract
767 - Sensitizing HRAS overexpressing head and neck squamous cell carcinoma (HNSCC) to chemotherapy
Presenter: Theodoros Rampias
Session: Poster Display session 3
Resources:
Abstract
4985 - A Single-Arm, Open-Label, Multicenter, Phase IIIb Clinical Trial with Nivolumab in Subjects with Recurrent or Metastatic Platinum-refractory Squamous Cell Carcinoma of the Head and Neck.
Presenter: Paolo Bossi
Session: Poster Display session 3
Resources:
Abstract
1564 - Long-term Results of Phase 2 Trial of Reduced Modified Clinical Target Volume in Low-risk Nasopharyngeal Carcinoma Treated with Intensity Modulated Radiotherapy
Presenter: Jingjing Miao
Session: Poster Display session 3
Resources:
Abstract
3356 - To compare two oral mucosa contouring methods in predicting acute oral mucocitis in nasopharyngeal carcinoma treated with helical tomotherapy
Presenter: Yuan-Yuan Chen
Session: Poster Display session 3
Resources:
Abstract
1984 - Induction chemotherapy (IC) followed by concurrent chemoradiotherapy (CCRT) in nasopharyngeal carcinoma (NPC)
Presenter: Gizem Kaval
Session: Poster Display session 3
Resources:
Abstract