Rigel Pharmaceuticals, Inc. – A Due Diligence

With high institutional ownership and with good phase 3 data, RIGL seems like a good choice to hold for the next year.


Rigel [NASDAQ:RIGL] is a pharmaceutical company that is currently working on a number of drugs in their pipeline, mostly hematological drugs.  It’s important I mention that out of all the drugs that are pending approval, hematological drugs tend to have a better chance than, say, oncological drugs.

Immune Thrombocytopenic Purpura [ITP]

Let’s discuss ITP for a second before we jump into Rigel’s pipeline.  Immune thrombocytopenic purpura occurs when a patient’s body attacks its own platelet supply, causing the number of platelets to decrease, and thus, causing petechiae (small tiny bruises), bruising, or even bleeding from the gums.  This is especially dangerous as a patient could suffer a traumatic incident such as a bump on the head or in a car accident, and the internal bleeding or intracerebral (brain) bleeding that would clot in a healthy person, would continue to bleed in a patient with ITP, causing fatal complications.

Diagnosing a patient with ITP is interesting, however, as the diagnosis is one of exclusion.  Several tests need to be performed in order to rule out other causes of low platelet counts (other blood disorders, cancer, medication, hepatitis, etc.) and bone marrow examination may also be required in order to rule out other diseases.

Currently, we don’t treat patients with low platelet counts unless they are symptomatic, and a dose of corticosteroids usually suppress the immune system and allow the platelet numbers to rise.  Other therapy options are RhoGAM, which are normally utilized in Rh – mothers with Rh + babies.  This drug, however, is not fully understood in terms of why it works for patients with ITP.  There are other immune suppressing therapies out there such as MMF or chemotherapy, but this sort of therapy, while being highly effective, is sparingly utilized due to its side effects.
There are currently thrombopoietin agonists that stimulate platelet production that are also available.


In comes fostamatinib, an oral spleen tyrosine kinase inhibitor. It essentially blocks the antibodies that attack the platelets so that it no longer recognizes the platelets, thus leading to no destruction.  Their phase 3 met primary endpoints, showing that out of 76 patients, 18% of the patients achieved a stable response compared to placebo (p = 0.0261).  These patients’ platelet count increased above 50,000/uL of blood.

They are currently researching fostamatinib for autoimmune hemolytic anemia, as well, with phase 2 data releasing end of 2017.

NDA for the ITP indication was submitted and is awaiting for approval PDUFA in April 17, 2018.


With high institutional ownership and with good phase 3 data, RIGL seems like a good choice to hold for the next year.  One thing that does concern me is the market size for ITP, as steroids are a good cheap treatment (though not perfect).


Disclosure Statement
I currently do not have any positions in RIGL.