Preclinical activity of ilmofosine against human tumor colony forming units in vitro

Ilmofosine (BM 41.440, 1-hexadecylthio-2-methoxymethyl-rac-glycero-3-phosphocholine) is a synthetic alkyl lysophospholipid analog with activity against a variety of tumor models in vitro and in vivo. The i.v. form is presently undergoing early clinical investigation in phase I trials. In order to help define types of tumors that might be clinically sensitive to this agent we have studied the anti-tumor effects of ilmofosine against a variety of freshly explanted human tumor specimens using an in vitro soft agar cloning system. Final concentrations of 1.0-30 microgram/ml were used in continuous incubations experiments. Of 348 specimens tested, 134 (39%) were evaluable for determination of tumor growth modulating activity. The most common tumor types recruited included non-small cell lung, breast, colorectal, ovarian, renal cell cancer and melanoma. A concentration-dependent increase in the frequency of inhibited tumor specimens was observed with 6/134 (4%) sensitive specimens at 1 microgram/ml as compared with 113/133 (85%) sensitive specimens at 30 micrograms/ml (p less than 0.0000005). We conclude that ilmofosine is active against a variety of tumors in vitro. Clinical phase II trials with ilmofosine including the tumor types with in vitro sensitivity are warranted if adequate plasma concentrations of this agent can be reached in patients.