Fears had earlier been raised that the Omicron variant of haemophilia might not be vulnerable to current blood-thinning drugs, but doctors are now reporting promising early results. The main problem with Omicron, currently approved as a prophylactic treatment for most forms of the disease, is that it is difficult to take and the risk of bleeding is high. Blood-thinning drugs such as Coumadin, warfarin and heparin, used for asymptomatic bleeding, have been a mainstay of blood-thinning treatment in the US, Europe and Japan for some years. However, U.S. doctors have come under pressure to make blood thinning drugs available to patients who should not be taking them. The main concern among doctors was that the main ingredient in Omicron, called apoC-III, might be unable to cross the blood-thinning blood cells. This could mean the drug was ineffective and fatal if someone needed bleeding to stop, particularly if they did not have an adequate blood supply. But some doctors have now said that early studies so far suggest the risk of bleeding in people on Omicron is low – about the same as for warfarin or heparin. The findings have been reported by a team led by medical scientist Zhe Yi, at Johns Hopkins University in Baltimore, Maryland. In more than 200 people on the treatment, significant bleeding was seen only in cases where blood was inaccessible. It was also less frequent than for other forms of haemophilia. Measurable benefit For blood-thinning treatment to be effective, the drugs must be able to cross the blood-thinning cells into the muscle – and in this way restore the clotting power of the blood. To give them sufficient distance, the effects need to be minimal. That is where this report comes in. Also known as Factor IX, the protein in haemophilia which can be effectively increased in Omicron is called apoC-III. The researchers note that the initial studies had already suggested that apoC-III particles had a small but detectable effect on clotting cells. However, the high dose of Omicron found to be effective – given in general as five or six to one – is extraordinarily potent. “When these effects are added together, there is a favorable risk-benefit ratio,” say the researchers, published in the journal Blood. Dr Zhe Yi said this achievement could mean haemophilia would no longer be a fatal illness in more than two thirds of cases. ‘Barriers to treatment’ The study also notes that extreme apoC-III levels should be considered before considering the increased amount of clotting. If the results continue to be reassuring, doctors could be expected to begin testing Omicron on a wider group of patients. Dr William Maisel, a haemophilia expert at the Imperial College in London, said the report was “encouraging”. But the potential benefits were still “very, very small”. He said he feared there would still be obstacles to doing this in the U.S. and he recommended careful assessment of the impact of oral Factor IX on the over-50s, and those who had blood disorders.
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