Legless, further to your statement regarding IgM antibodies"All...

Legless, further to your statement regarding IgM antibodies

"All the antibodies on the market today come from the IgG class. In order to create such drugs there are many enabling technologies for which high royalties are payable. For new IgM antibodies the royalty stack would be low. Patrys argues that their IgM antibodies are also more effective in terms of their binding ability."

"IgM antibodies can be better than IgG antibodies. IgM antibodies only comprise 5-10% of all the antibodies in the body, but they are arguably the immune system’s ‘antibody of choice’ as part of the innate immune system. Whenever the immune system encounters an antigen for the first time it rapidly creates IgM antibodies whereas IgG antibodies take a lot longer to make and are therefore primarily active during a secondary immune response. IgM antibodies are ideal for a primary immune response because their pentameric structure – five immunoglobulin proteins complexed together – enables the simultaneous binding of many antigens, allowing their rapid clearance from the bloodstream. This simultaneous binding capability suggests that IgMs would make great drugs if easily available.”

Sum: cheaper to make IgM (e.g. SM26) than IgG antibodies
Source: Bellpotter review