I am not a scientist and I am really not sure. But it appears that there are a number of factors at play:
1. Several companies, sometimes even Halo's partners (Roche, Alexion, probably others too), seem to be able to develop their own SC formulations.
2. My understanding is that Halo's partners get exclusive access to Enhanze for any product with a specific target. For instance, "The agreement provides argenx exclusive access to ENHANZE® for any product targeting the human neonatal Fc receptor FcRn, including argenx's lead asset efgartigimod (ARGX-113)". It's conceivable that some companies are mostly interested in preventing competitors from developing SC formulations with Enhanze in a specific target (perhaps Pfizer and Abbvie) and more inclined to push their IV formulations than sharing revenues with Halo (perhaps Roche with Herceptin and Mabthera).
3. I think doctors and hospitals have financial incentives to use IV formulations rather than SC formulations.
It seems the stars have perfectly aligned for Halo with Darzalex FasPro. Janssen probably used Enhanze to prevent competitors from using it to develop SC formulations targeting the CD 38 protein but the benefits are so dramatic that they also help fend off competing drugs so it would make no sense for Janssen to push their IV formulation of Darzalex. The huge shortening of the drug administration time also make it impossible for doctors and hospitals not to offer it to patients. The icing on the cake for Janssen (and Halo) is that for now Janssen is sharing with Genmab the cost of Halo's royalties.
This is as good as it gets and I fear it won't happen again. The best I am able to hope for is that we have 5 or 6 products in phase 3 trials by the end of the year, 2 or 3 new products approved by the end of 2023 and 2 more by the end of 2025. This could mean $600M in royalties plus perhaps $100M in milestone payments per year by then. If this becomes likely, will PPS get to $100 within a year or so? Maybe. The other wild card of course is the potential of an acquisition. It's really hard to predict whether that will help or hurt the stock.
