A phase I study of the P-glycoprotein antagonist tariquidar in combination with vinorelbine.
OBJECTIVE
P-glycoprotein (Pgp) antagonists have had unpredictable pharmacokinetic interactions requiring reductions of chemotherapy. We report a phase I study using tariquidar (XR9576), a potent Pgp antagonist, in combination with vinorelbine.


METHODS
Patients first received tariquidar alone to assess effects on the accumulation of (99m)Tc-sestamibi in tumor and normal organs and rhodamine efflux from CD56+ mononuclear cells. In the first cycle, vinorelbine pharmacokinetics was monitored after the day 1 and 8 doses without or with tariquidar. In subsequent cycles, vinorelbine was administered with tariquidar. Tariquidar pharmacokinetics was studied alone and with vinorelbine.


RESULTS
Twenty-six patients were enrolled. Vinorelbine 20 mg/m(2) on day 1 and 8 was identified as the maximum tolerated dose (neutropenia). Nonhematologic grade 3/4 toxicities in 77 cycles included the following: abdominal pain (4 cycles), anorexia (2), constipation (2), fatigue (3), myalgia (2), pain (4) and dehydration, depression, diarrhea, ileus, nausea, and vomiting, (all once). A 150-mg dose of tariquidar: (1) reduced liver (99m)Tc-sestamibi clearance consistent with inhibition of liver Pgp; (2) increased (99m)Tc-sestamibi retention in a majority of tumor masses visible by (99m)Tc-sestamibi; and (3) blocked Pgp-mediated rhodamine efflux from CD56+ cells over the 48 hours examined. Tariquidar had no effects on vinorelbine pharmacokinetics. Vinorelbine had no effect on tariquidar pharmacokinetics. One patient with breast cancer had a minor response, and one with renal carcinoma had a partial remission.


CONCLUSIONS
Tariquidar is a potent Pgp antagonist, without significant side effects and much less pharmacokinetic interaction than previous Pgp antagonists. Tariquidar offers the potential to increase drug exposure in drug-resistant cancers.
Mary Babb Cancer Center, University of West Virginia, Morgantown, WV, USA.
Jame
J
Abraham
Maureen
M
Edgerly
Richard
R
Wilson
Clara
C
Chen
Ann
A
Rutt
Susan
S
Bakke
Rob
R
Robey
Andrew
A
Dwyer
Barry
B
Goldspiel
Frank
F
Balis
Olaf
O
Van Tellingen
Susan E
SE
Bates
Tito
T
Fojo
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000972:Antineoplastic Agents, Phytogenic / Q000009:adverse effects / Q000493:pharmacokinetics; D019540:Area Under Curve; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D006801:Humans; D008657:Metabolic Clearance Rate; D008875:Middle Aged; D009369:Neoplasms / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D009503:Neutropenia / Q000139:chemically induced; D011804:Quinolines / Q000009:adverse effects / Q000493:pharmacokinetics*; D014747:Vinblastine / Q000009:adverse effects / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D000077235:Vinorelbine; D055815:Young Adult
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000972:Antineoplastic Agents, Phytogenic; D011804:Quinolines; D014747:Vinblastine; C402343:tariquidar; D000077235:Vinorelbine