Electrocardiogram studies on cancer patients treated with OK-432, a streptococcal preparation with potent biological response modifier activities.

The present study was performed to see if OK-432, a useful anticancer agent with potent biological response modifier activities, induces effects on heart due to its nature as a streptococcal preparation. Examination of electrocardiograms of cancer patients treated with a variety of doses and routes of OK-432 has revealed that none of 266 patients examined showed any significant change in electrocardiograms (ECGs) after OK-432 treatments, regardless of their pretreatment heart conditions (normal or abnormal ECGs). Furthermore, these patients did not develop any detectable antibodies against heart muscle, either in serum or deposited on heart tissue. Experimentally, antibodies reactive with human heart tissue became detectable in the sera of rabbits immunized with streptococci in complete Freund's adjuvant, confirming the previous reports. However, the repeated injections of OK-432 without the adjuvant did not induce any detectable antibodies. These results indicate that OK-432 can be used for treating cancer patients with little fear of possible side effects on the heart.