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Clinical Studies

Phase I study of procaspase-activating compound-1 (PAC-1) in the treatment of advanced malignancies



Procaspase-3 (PC-3) is overexpressed in multiple tumour types and procaspase-activating compound 1 (PAC-1) directly activates PC-3 and induces apoptosis in cancer cells. This report describes the first-in-human, phase I study of PAC-1 assessing maximum tolerated dose, safety, and pharmacokinetics.


Modified-Fibonacci dose-escalation 3 + 3 design was used. PAC-1 was administered orally at 7 dose levels (DL) on days 1–21 of a 28-day cycle. Dose-limiting toxicity (DLT) was assessed during the first two cycles of therapy, and pharmacokinetics analysis was conducted on days 1 and 21 of the first cycle. Neurologic and neurocognitive function (NNCF) tests were performed throughout the study.


Forty-eight patients were enrolled with 33 completing ≥2 cycles of therapy and evaluable for DLT. DL 7 (750 mg/day) was established as the recommended phase 2 dose, with grade 1 and 2 neurological adverse events noted, while NNCF testing showed stable neurologic and cognitive evaluations. PAC-1’s t1/2 was 28.5 h after multi-dosing, and systemic drug exposures achieved predicted therapeutic concentrations. PAC-1 clinical activity was observed in patients with neuroendocrine tumour (NET) with 2/5 patients achieving durable partial response.


PAC-1 dose at 750 mg/day was recommended for phase 2 studies. Activity of PAC-1 in treatment-refractory NET warrants further investigation.

Clinical trial registration

Clinical NCT02355535.

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Fig. 1: Pharmacokinetics of PAC-1.
Fig. 2: Duration of therapy and response to treatment at different dose levels.
Fig. 3: Procaspase-3 (PC-3) expressions in diverse tumour histologies categorised as moderate-to-strong immunostaining intensities.

Data availability

The data generated in this study are available upon request from the corresponding author.


  1. Dix MM, Simon GM, Cravatt BF. Global mapping of the topography and magnitude of proteolytic events in apoptosis. Cell. 2008;134:679–91.

    Article  CAS  Google Scholar 

  2. Mahrus S, Trinidad JC, Barkan DT, Sali A, Burlingame AL, Wells JA. Global sequencing of proteolytic cleavage sites in apoptosis by specific labeling of protein N termini. Cell. 2008;134:866–76.

    Article  CAS  Google Scholar 

  3. Boudreau MW, Peh J, Hergenrother PJ. Procaspase-3 overexpression in cancer: a paradoxical observation with therapeutic potential. ACS Chem Biol. 2019;14:2335–48.

    Article  CAS  Google Scholar 

  4. Putt KS, Chen GW, Pearson JM, Sandhorst JS, Hoagland MS, Kwon JT, et al. Small-molecule activation of procaspase-3 to caspase-3 as a personalized anticancer strategy. Nat Chem Biol. 2006;2:543–50.

    Article  CAS  Google Scholar 

  5. Peterson QP, Hsu DC, Goode DR, Novotny CJ, Totten RK, Hergenrother PJ. Procaspase-3 activation as an anti-cancer strategy: structure-activity relationship of procaspase-activating compound 1 (PAC-1) and its cellular co-localization with caspase-3. J Med Chem. 2009;52:5721–31.

    Article  CAS  Google Scholar 

  6. Peterson QP, Goode DR, West DC, Ramsey KN, Lee JJY, Hergenrother PJ. PAC-1 activates procaspase-3 in vitro through relief of zinc-mediated inhibition. J Mol Biol. 2009;388:144–58.

    Article  CAS  Google Scholar 

  7. Truong-Tran AQ, Grosser D, Ruffin RE, Murgia C, Zalewski PD. Apoptosis in the normal and inflamed airway epithelium: role of zinc in epithelial protection and procaspase-3 regulation. Biochem Pharm. 2003;66:1459–68.

    Article  CAS  Google Scholar 

  8. West DC, Qin Y, Peterson QP, Thomas DL, Palchaudhuri R, Morrison KC, et al. Differential effects of procaspase-3 activating compounds in the induction of cancer cell death. Mol Pharm. 2012;9:1425–34.

    Article  CAS  Google Scholar 

  9. Putinski C, Abdul-Ghani M, Stiles R, Brunette S, Dick SA, Fernando P, et al. Intrinsic-mediated caspase activation is essential for cardiomyocyte hypertrophy. Proc Natl Acad Sci USA. 2013;110:E4079–87.

    Article  CAS  Google Scholar 

  10. Wang F, Wang L, Zhao Y, Li Y, Ping G, Xiao S, et al. A novel small-molecule activator of procaspase-3 induces apoptosis in cancer cells and reduces tumor growth in human breast, liver and gallbladder cancer xenografts. Mol Oncol. 2014;8:1640–52.

    Article  CAS  Google Scholar 

  11. Seervi M, Sobhan PK, Mathew KA, Joseph J, Pillai PR, Santhoshkumar TR. A high-throughput image-based screen for the identification of Bax/Bak-independent caspase activators against drug-resistant cancer cells. Apoptosis. 2014;19:269–84.

    Article  CAS  Google Scholar 

  12. Monaco G, Decrock E, Akl H, Ponsaerts R, Vervliet T, Luyten T, et al. Selective regulation of IP3-receptor-mediated Ca2+ signaling and apoptosis by the BH4 domain of Bcl-2 versus Bcl-Xl. Cell Death Differ. 2012;19:295–309.

    Article  CAS  Google Scholar 

  13. Patel V, Balakrishnan K, Keating MJ, Wierda WG, Gandhi V. Expression of executioner procaspases and their activation by a procaspase-activating compound in chronic lymphocytic leukemia cells. Blood. 2015;125:1126–36.

    Article  CAS  Google Scholar 

  14. Zhao HJ, Liu T, Mao X, Han S, Liang R, Hui L, et al. Fructus phyllanthi tannin fraction induces apoptosis and inhibits migration and invasion of human lung squamous carcinoma cells in vitro via MAPK/MMP pathways. Acta Pharmacol Sin. 2015;36:758–68.

    Article  CAS  Google Scholar 

  15. Ma J, Bao G, Wang L, Li W, Xu B, Du B, et al. Design, synthesis, biological evaluation and preliminary mechanism study of novel benzothiazole derivatives bearing indole-based moiety as potent antitumor agents. Eur J Med Chem. 2015;96:173–86.

    Article  CAS  Google Scholar 

  16. Chakkath T, Lavergne SN, Fan TM, Bunick D, Dirikolu L. Preliminary metabolism of lomustine in dogs and comparative cytotoxicity of lomustine and its major metabolites in canine cells. Vet Sci. 2014;1:159–73.

    Article  Google Scholar 

  17. Guo WT, Wang XW, Yan YL, Li YP, Yin X, Zhang Q, et al. Suppression of epithelial-mesenchymal transition and apoptotic pathways by miR-294/302 family synergistically blocks let-7-induced silencing of self-renewal in embryonic stem cells. Cell Death Differ. 2015;22:1158–69.

    Article  CAS  Google Scholar 

  18. Xu J, Li Z, Wang J, Chen H, Fang JY. Combined PTEN mutation and protein expression associate with overall and disease-free survival of glioblastoma patients. Transl Oncol. 2014;7:196–205.

    Article  Google Scholar 

  19. Campbell DS, Okamoto H. Local caspase activation interacts with Slit-Robo signaling to restrict axonal arborization. J Cell Biol. 2013;203:657–72.

    Article  CAS  Google Scholar 

  20. Zhu H, Sun G, Dong J, Fei L. The role of PRRX1 in the apoptosis of A549 cells induced by cisplatin. Am J Transl Res. 2017;9:396–402.

    CAS  Google Scholar 

  21. Dong T, Zhang Q, Hamblin MR, Wu MX. Low-level light in combination with metabolic modulators for effective therapy of injured brain. J Cereb Blood Flow Metab. 2015;35:1435–44.

    Article  CAS  Google Scholar 

  22. Dick SA, Chang NC, Dumont NA, Bell RAV, Putinski C, Kawabe Y, et al. Caspase 3 cleavage of Pax7 inhibits self-renewal of satellite cells. Proc Natl Acad Sci USA. 2015;112:E5246–52.

    Article  CAS  Google Scholar 

  23. Xu L, Zeng Z, Zhang W, Ren G, Ling X, Huang F, et al. RXRα ligand Z-10 induces PML-RARα cleavage and APL cell apoptosis through disrupting PML-RARα/RXRα complex in a cAMP-independent manner. Oncotarget. 2017;8:12311–22.

    Article  Google Scholar 

  24. Namjoshi P, Showalter L, Czerniecki BJ, Koski GK. T-helper 1-type cytokines induce apoptosis and loss of HER-family oncodriver expression in murine and human breast cancer cells. Oncotarget. 2019;10:6006–20.

    Article  Google Scholar 

  25. Auner HW, Beham-Schmid C, Dillon N, Sabbattini P. The life span of short-lived plasma cells is partly determined by a block on activation of apoptotic caspases acting in combination with endoplasmic reticulum stress. Blood. 2010;116:3445–55.

    Article  CAS  Google Scholar 

  26. Wang H, Boussouar A, Mazelin L, Tauszig-Delamasure S, Sun Y, Goldschneider D, et al. The proto-oncogene c-Kit inhibits tumor growth by behaving as a dependence receptor. Mol Cell. 2018;72:413–25.

    Article  CAS  Google Scholar 

  27. Yosefzon Y, Soteriou D, Feldman A, Kostic L, Koren E, Brown S, et al. Caspase-3 regulates YAP-dependent cell proliferation and organ size. Mol Cell. 2018;70:573–87.e4.

    Article  CAS  Google Scholar 

  28. Chen Y, Sun M, Ding J, Zhu Q. SM-1, a novel PAC-1 derivative, activates procaspase-3 and causes cancer cell apoptosis. Cancer Chemother Pharm. 2016;78:643–54.

    Article  CAS  Google Scholar 

  29. Zhai X, Bao G, Wang L, Cheng M, Zhao M, Zhao S, et al. Design, synthesis and biological evaluation of novel 4-phenoxy-6,7-disubstituted quinolines possessing (thio)semicarbazones as c-Met kinase inhibitors. Bioorg Med Chem. 2016;24:1331–45.

    Article  CAS  Google Scholar 

  30. Ma J, Chen D, Lu K, Wang L, Han X, Zhao Y, et al. Design, synthesis, and structure-activity relationships of novel benzothiazole derivatives bearing the ortho-hydroxy N-carbamoylhydrazone moiety as potent antitumor agents. Eur J Med Chem. 2014;86:257–69.

    Article  CAS  Google Scholar 

  31. Ma J, Zhang G, Han X, Bao G, Wang L, Zhai X. et al. Synthesis and biological evaluation of benzothiazole derivatives bearing the ortho-hydroxy-N-acylhydrazone moiety as potent antitumor agents. Arch Pharm. 2014;347:936–49.

    Article  CAS  Google Scholar 

  32. Wang F, Wang L, Li Y, Wang N, Wang Y, Cao Q, et al. PAC-1 and its derivative WF-210 inhibit angiogenesis by inhibiting VEGF/VEGFR pathway. Eur J Pharm. 2018;821:29–38.

    Article  CAS  Google Scholar 

  33. Botham RC, Fan TM, Im I, Borst LB, Dirikolu L, Hergenrother PJ. Dual small-molecule targeting of procaspase-3 dramatically enhances zymogen activation and anticancer activity. J Am Chem Soc. 2014;136:1312–9.

    Article  CAS  Google Scholar 

  34. Peh J, Fan TM, Wycislo KL, Roth HS, Hergenrother PJ. The combination of vemurafenib and procaspase-3 activation is synergistic in mutant BRAF melanomas. Mol Cancer Ther. 2016;15:1859–69.

    Article  CAS  Google Scholar 

  35. Botham RC, Roth HS, Book AP, Roady PJ, Fan TM, Hergenrother PJ. Small-molecule procaspase-3 activation sensitizes cancer to treatment with diverse chemotherapeutics. ACS Cent Sci. 2016;2:545–59.

    Article  CAS  Google Scholar 

  36. Lucas PW, Schmit JM, Peterson QP, West DC, Hsu DC, Novotny CJ, et al. Pharmacokinetics and derivation of an anticancer dosing regimen for PAC-1, a preferential small molecule activator of procaspase-3, in healthy dogs. Invest N Drugs. 2011;29:901–11.

    Article  CAS  Google Scholar 

  37. Joshi AD, Botham RC, Schlein LJ, Roth HS, Mangraviti A, Borodovsky A, et al. Synergistic and targeted therapy with a procaspase-3 activator and temozolomide extends survival in glioma rodent models and is feasible for the treatment of canine malignant glioma patients. Oncotarget. 2017;8:80124–38.

    Article  Google Scholar 

  38. Schlein LJ, Fadl-Alla B, Pondenis HC, Lezmi S, Eberhart CG, LeBlanc AK, et al. Immunohistochemical characterization of procaspase-3 overexpression as a druggable target with PAC-1, a procaspase-3 activator, in canine and human brain cancers. Front Oncol. 2019;9:96.

    Article  Google Scholar 

  39. Tonogai EJ, Huang S, Botham RC, Berry MR, Joslyn SK, Daniel GB, et al. Evaluation of a procaspase-3 activator with hydroxyurea or temozolomide against high-grade meningioma in cell culture and canine cancer patients. Neuro Oncol. 2021;23:1723–35.

    Article  CAS  Google Scholar 

  40. Eisenhauer EA, Therasse P, Bogaerts J, Schwartz LH, Sargent D, Ford R, et al. New response evaluation criteria in solid tumours: revised RECIST guideline (version 1.1). Eur J Cancer. 2009;45:228–47.

    Article  CAS  Google Scholar 

  41. USDHHS. Common Terminology Criteria for Adverse Events (CTCAE) Version 4.0. 2010.

  42. Spencer MPF, Folstein MF. The Mini-Mental State Examination. In: Keller PAR, Ritt LG (eds). Innovations in clinical practice: a source book. Sarasota, FL: Professional Resource Exchange, Inc.; 1985) pp 307–8.

  43. Shapiro AM, Benedict RH, Schretlen D, Brandt J. Construct and concurrent validity of the Hopkins Verbal Learning Test-revised. Clin Neuropsychol. 1999;13:348–58.

    Article  CAS  Google Scholar 

  44. Brandt J, Benedict R. Hopkins Verbal Learning Test-revised. Lutz, FL: Psychological Assessment Resources, Inc.; 2001.

  45. Benedict RHB, Schretlen D, Groninger L, Brandt J. Hopkins Verbal Learning Test-Revised: Normative data and analysis of inter-form and test-retest reliability. Clin Neuropsychol. 1998;12:43–55.

    Article  Google Scholar 

  46. Reitan R. Manual for administration of neuropsychological test batteries for adults and children. Tucson, AZ: Reitan Neuropsychology Laboratories; 1978.

  47. Levine AJ, Miller EN, Becker JT, Selnes OA, Cohen BA. Normative data for determining significance of test-retest differences on eight common neuropsychological instruments. Clin Neuropsychol. 2004;18:373–84.

    Article  Google Scholar 

  48. Benton AL, Hamsher KD, Siva AB. Multilingual aphasia examination. Lutz, FL: Psychological Assessment Resources, Inc; 1994.

    Google Scholar 

  49. Ruff RM, Light RH, Parker SB, Levin HS. Benton Controlled Oral Word Association Test: reliability and updated norms. Arch Clin Neuropsychol. 1996;11:329–38.

    Article  CAS  Google Scholar 

  50. Wefel JS, Vardy J, Ahles T, Schagen SB. International Cognition and Cancer Task Force recommendations to harmonise studies of cognitive function in patients with cancer. Lancet Oncol. 2011;12:703–8.

    Article  Google Scholar 

  51. Neurocognitive Test Summary provided by the Health Services and Research Outcomes (HSRO) Subcommittee of the Radiation Therapy Oncology Group (RTOG). 2011.

  52. Jacobson NS, Truax P. Clinical significance: a statistical approach to defining meaningful change in psychotherapy research. J Consult Clin Psychol. 1991;59:12–9.

    Article  CAS  Google Scholar 

  53. Wefel JS, Cloughesy T, Zazzali JL, Zheng M, Prados M, Wen PY, et al. Neurocognitive function in patients with recurrent glioblastoma treated with bevacizumab. Neuro Oncol. 2011;13:660–8.

    Article  CAS  Google Scholar 

  54. Raymond E, Dahan L, Raoul JL, Bang YJ, Borbath I, Lombard-Bohas C, et al. Sunitinib malate for the treatment of pancreatic neuroendocrine tumors. N Engl J Med. 2011;364:501–13.

    Article  CAS  Google Scholar 

  55. Peh J, Boudreau MW, Smith HM, Hergenrother PJ. Overcoming resistance to targeted anticancer therapies through small-molecule-mediated MEK degradation. Cell Chem Biol. 2018;25:996.e4–1005.e4.

    Article  Google Scholar 

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We thank James P. Zacny, PhD for his editorial support with the clinical protocol and manuscript. LC-MS/MS was performed at the Toxicology Research Laboratory, College of Medicine at the University of Illinois at Chicago. We thank the patients who participated and the Clinical Trials Office of the University of Illinois Cancer Center for providing the necessary clinical research infrastructure to execute this study.


Financial support was provided by Vanquish Oncology. Inc., the University of Illinois Cancer Center, the University of Illinois, the NIH (R01CA120439), and Engdahl Family Foundation.

Author information

Authors and Affiliations



AZD and OCD designed the study. OCD, MH, RAP, NKV, and MJR acquired the data. OCD, MH, RAP, and NKV provided RECIST assessments. JHF did the pharmacokinetic testing. LCL did the statistical analysis. AZD, PJH, TMF, TMT, and OCD provided data analysis. AZD and OCD prepared the initial draft of the manuscript. Revisions were prepared by AZD, PJH, TMF, TMT, and OCD. All authors contributed to subsequent manuscript drafts and agreed with the submission of the manuscript for publication.

Corresponding author

Correspondence to Oana C. Danciu.

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Competing interests

PJH serves as Chief Scientific Officer and has equity in Vanquish Oncology, Inc. TMT serves as Chief Executive Officer and has equity in Vanquish Oncology, Inc. TMF serves as VP Preclinical Development and has equity in Vanquish Oncology, Inc. AZD reports research funding from Eli Lilly. AZD served as Chief Medical Officer for Vanquish Oncology, Inc. AZD serves as Chief Executive Officer for TTC Oncology, LLC, and Chief Medical Officer for IGF Oncology. All other authors declare no competing interests.

Ethics approval and consent to participate

The study was conducted according to International Conference on Harmonisation of Good Clinical Practice guidelines and the principles of the Declaration of Helsinki. The protocol was approved by the Institutional Review Board/Ethics Committee at each study location. All patients provided written informed consent before enrolment.

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Not applicable.

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Danciu, O.C., Holdhoff, M., Peterson, R.A. et al. Phase I study of procaspase-activating compound-1 (PAC-1) in the treatment of advanced malignancies. Br J Cancer (2022).

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