CytomX had their R&D Day on February 26th, 2019.  They subsequently released earnings on February 27th, 2019.  There were a bunch of negatives and a few positives.  Let's discuss the negatives first:

  • Bristol Myers decided to stop R&D on 3 partnered targets
  • CX-2009 was relatively toxic at high doses with no confirmed responses

The Bristol Myers collaboration included 12 targets (4 initially and 8 with expansion).  3 Targets is only 25% of the collaboration and more reflective of portfolio optimization then an issue with probody technology.  Importantly the BMS-986249 (CTLA-4) is still ongoing and has added additional sites recently.  The CTLA-4 probody read out this year is extremely important for the probody platform.

CX-2009 is a PDC (Probody Drug Conjugate) using Immunogen's linker/toxin (DM4).   Unfortunately, DM4 has significant off-target effects and although active is not very efficacious and has issues with its survival benefit.  The side effects at the high doses of CX-2009 were mostly related to the known off-target effects of DM4 and will be better characterized at an upcoming presentation in April at the AACR conference.

Immunogen announced the failure of their own late stage study of their DM4 candidate for ovarian cancer proving that their linker/toxin is subpar.  

Luckily for CytomX they were able to partner with Abbvie to access Seattle Genetics MMAE toxin for CX-2029.   Unfortunately the data presentation for CX-2029 is still probably a year away and therefore won't provide any stock support anytime soon.  CX-2029 also targets CD-71 which is one of the best possible targets for an ADC.

Embedded within the negatives was the positive that in 50 patients dosed at 10 mg/k of CX-072 (PD-L1) monotherapy there were only 2 grade 3 irAE's and 0 discontinuations.  The PD-L1 probody continues to be much safer than other PD pathway inhibitors especially in combination.  A Probody/Probody combination of PD-L1 and CTLA-4 probody could provide a competitive edge for Bristol in the immunotherapy wars.

Unfortunately CTMX is now a 2020 story.  I sold 1/2 at the open on R&D day and 80% of the remaining position the day after when there was 0 bounce.  The money was re-invested in SGMO (Sangamo) which has many more potential positives for the remainder of 2019 and should perform significantly better.  

When CTMX is ready to announce CX-2029 data, it should be a good time to re-build a position.    Still long term positive on CTMX.  However,  SGMO provides much more upside in 2019 and hopefully will offset losses here.