title: Phase I and pharmacokinetic study of D-limonene in patients with advanced cancer. Cancer Research Campaign Phase I/II Clinical Trials Committee.
abstract: OBJECTIVE
  D-Limonene is a natural monoterpene with pronounced chemotherapeutic activity and minimal toxicity in preclinical studies. A phase I clinical trial to assess toxicity, the maximum tolerated dose (MTD) and pharmacokinetics in patients with advanced cancer was followed by a limited phase II evaluation in breast cancer.
  
  
  METHODS
  A group of 32 patients with refractory solid tumors completed 99 courses of D-limonene 0.5 to 12 g/m2 per day administered orally in 21-day cycles. Pharmacokinetics were analyzed by liquid chromatography-mass spectrometry. Ten additional breast cancer patients received 15 cycles of D-limonene at 8 g/m2 per day. Intratumoral monoterpene levels were measured in two patients.
  
  
  RESULTS
  The MTD was 8 g/m2 per day; nausea, vomiting and diarrhea were dose limiting. One partial response in a breast cancer patient on 8 g/m2 per day was maintained for 11 months; three patients with colorectal carcinoma had prolonged stable disease. There were no responses in the phase II study. Peak plasma concentration (Cmax) for D-limonene ranged from 10.8+/-6.7 to 20.5+/-11.2 microM. Predominant circulating metabolites were perillic acid (Cmax 20.7+/-13.2 to 71+/-29.3 microM), dihydroperillic acid (Cmax 16.6+/-7.9 to 28.1+/-3.1 microM), limonene-1,2-diol (Cmax 10.1+/-8 to 20.7+/-8.6 microM), uroterpenol (Cmax 14.3+/-1.5 to 45.1+/-1.8 microM), and an isomer of perillic acid. Both isomers of perillic acid, and cis and trans isomers of dihydroperillic acid were in urine hydrolysates. Intratumoral levels of D-limonene and uroterpenol exceeded the corresponding plasma levels. Other metabolites were trace constituents in tissue.
  
  
  CONCLUSIONS
  D-Limonene is well tolerated in cancer patients at doses which may have clinical activity. The favorable toxicity profile supports further clinical evaluation.
authors.affiliation: Department of Medical Oncology, Charing Cross Hospital, London, UK. d.vigushin@cxwms.ac.uk
authors.forename: D M
authors.initials: DM
authors.lastname: Vigushin
authors.forename: G K
authors.initials: GK
authors.lastname: Poon
authors.forename: A
authors.initials: A
authors.lastname: Boddy
authors.forename: J
authors.initials: J
authors.lastname: English
authors.forename: G W
authors.initials: GW
authors.lastname: Halbert
authors.forename: C
authors.initials: C
authors.lastname: Pagonis
authors.forename: M
authors.initials: M
authors.lastname: Jarman
authors.forename: R C
authors.initials: RC
authors.lastname: Coombes
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000972:Antineoplastic Agents, Phytogenic / Q000008:administration & dosage / Q000009:adverse effects / Q000378:metabolism / Q000493:pharmacokinetics*; D053138:Cyclohexenes; D005260:Female; D006801:Humans; D000077222:Limonene; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000188:drug therapy / Q000378:metabolism*; D013729:Terpenes / Q000008:administration & dosage / Q000009:adverse effects / Q000378:metabolism / Q000493:pharmacokinetics*; D016896:Treatment Outcome
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D053138:Cyclohexenes; D013729:Terpenes; D000077222:Limonene