Until 2014, very few options were available to treat ovarian cancer and these primarily included chemotherapy, radiation or surgery. Though effective, these treatments had many side-effects. While chemotherapy can destroy a patient’s immune system, radiation kills normal cells along with cancerous cells. A surgical process is ineffective when the cancer spreads. With the approval of AstraZeneca AZN/Merck’s MRK Lynparza in December 2014, a new targeted therapy for treating ovarian cancer came into the market. The drug inhibits an enzyme in cells – PARP – which helps repair the DNA of the cell, thus destroying the cell.
After that, two other PARP-inhibitors were approved by the FDA - Tesaro, Inc.’s TSRO Zejula and Clovis Oncology, Inc.’s CLVS Rubraca. PARP inhibitors have shown more tolerability and effectiveness in clinical studies. However, none of the three marketed PARP inhibitors – Rubraca, Zejula and Lynparza – have been approved in the first-line setting to date.
There are many other companies developing PARP inhibitors including Pfizer Inc. PFE and AbbVie Inc. ABBV, among others.
Let’s see how the marketed drugs are performing and which one has better prospects.
Lynparza with its recent label expansion in August 2017 is indicated for maintenance treatment of patients suffering from platinum-sensitive recurrent (“PSR”) ovarian cancer regardless of BRCA-mutation status. It is also approved for BRCA-mutated ovarian cancer beyond the third-line setting. The drug is available in capsule and tablet formulations. The drug recorded sales of $70 million in 2015, $94 million in 2016 and $197 million in the first nine months of 2017, growing over 65% annually. The drug is also being developed as first-line maintenance treatment for BRCA-mutated ovarian cancer. AstraZeneca and Merck expect to file for label expansion by mid-2018.
However, Lynparza sales have fallen lately in the United States after the launch of Zejula in April this year. The label expansion in August – including ovarian cancer patients regardless of BRCA-mutation – has brought it on par with Zejula. Moreover, a potential approval in first-line setting next year will give it an edge over the other drugs. Also, AstraZeneca has collaborated with Merck to co-develop Lynparza in combination immunotherapies. Its successful development will be a boon for patients.
Rubraca received accelerated approval from the FDA late last year as monotherapy in advanced ovarian cancer patients with deleterious BRCA mutation, treated with two or more chemotherapies. Clovis is conducting confirmatory studies to convert this approval to a full approval. Meanwhile, the company filed a supplemental New Drug Application last month, seeking label expansion as a maintenance treatment for patients with PSR ovarian cancer. Rubraca is under review in EU. The drug reported sales of $38.5 million in the first nine months of 2017. However, the drug may lag the other two drugs as they are approved to treat ovarian cancer irrespective of the BRCA-mutation. Meanwhile, Clovis is evaluating the drug in a phase III study in combination with Bristol-Myers’ BMY Opdivo as first-line maintenance therapy in stage III/IV high-grade ovarian cancer patients who were treated with platinum-based chemotherapy.
Zejula is the first PARP-inhibitor, which was approved as maintenance treatment for recurrent ovarian cancer regardless of BRCA-mutation and was launched in April 2017. As the drug can be used in patients who do not have BRCA mutations, it can be prescribed to a broader patient population. Moreover, it also removes the requirement of diagnosis for BRCA-mutation, thereby reducing treatment cost and time.
Due to this competitive advantage, Zejula has registered impressive growth since its launch and has also encroached upon Lynparza & Rubraca’s market share. The drug has generated sales of $65.3 million since its launch. The company has also claimed that it is the most frequently prescribed PARP inhibitor for ovarian cancer. Further boosting the prospect of the drug, the European Commission granted marketing authorization earlier this week. TESARO is also developing Zejula in combination with Merck’s anti-PD-1 drug, Keytruda, in patients with platinum-resistant ovarian cancer.
From the above discussion, it is evident that Zejula has an edge due to non-requirement of BRCA-mutation status and has fared better thus far. However, with an expanded label, Lynparza is set to get back its lost share. We believe that Rubraca could be in a relatively weaker position among the three drugs. There is uncertainty over how it performs in Europe as both Lynparza and Zejula are already approved there. However, we have to wait till 2018 end to see the actual performance of these drugs as a few label expansions are expected next year.
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