Major readouts on the horizon for small developers

Having already looked at the key second-quarter clinical data for big pharma and large biotech groups, Evaluate Vantage moves on to developers with a market cap under $1bn.

Platinum-resistant ovarian cancer is in the sights of Immunogen and Mersana, with both relying on specific biomarkers. The former is due to report confirmatory data with its antibody drug conjugate Elahere, while Mersana will release what it hopes will be registrational results with its ADC upifitamab rilsodotin. Elsewhere, a mid-stage readout is anticipated from Disc Medicine’s big pharma castoff bitopertin in porphyria, a rare metabolic disorder.

Immunogen’s endgame 

Immunogen’s Elahere became the first antibody-drug conjugate to be approved for ovarian cancer last year, when it gained an accelerated green light in second to fourth-line folate receptor alpha (FRα)-high platinum-resistant disease. Confirmatory results from the Mirasol study, to turn that into full approval, are pending. 

The trial sets Elahere against chemotherapy, with a primary endpoint of progression-free survival; Mirasol is designed to detect a hazard ratio of 0.7. Assuming 3.5 months of median PFS in the chemotherapy arm, median PFS needs to reach 5 months in the Elahere-treated cohort for the trial to succeed, analysts estimate. 

In Soraya, the single-cohort trial used to gain accelerated approval, median PFS hit 5.5 months by independent central review, but only 4.3 months by investigator assessment. Immunogen has pointed out that Soraya was in a more heavily treated population than Mirasol. Looking to another study, the controlled Forward I, the FRα-high subgroup showed Elahere to confer a 1.9 to 2.4-month median PFS benefit. 

Followers of Sutro will be keenly awaiting Immunogen’s confirmatory data. Luveltamab tazevibulin, Sutro is also hoping to take its less advanced antibody drug conjugate down the accelerated approval path. Sutro claims this asset can address a broader population than Elahere, as well as being safer. Elahere’s label comes with a black boxed warning about ocular toxicities. 

Uplift for Mersana? 

Sticking with platinum resistant ovarian cancer (PROC), registrational data are due from Mersana’s upifitamab rilsodotin. The ADC targets NaPi2b, a sodium-dependent phosphate transporter which is highly expressed in ovarian cancer and non-squamous NSCLC. 

Results from a pivotal cohort of the phase 2 Uplift study are due, in second to fourth-line PROC. The primary endpoint of the single arm study is confirmed ORR in NaPi2b-high patients. ORR in all patients, regardless of NaPi2b expression, is a secondary measure. 

The dose to report will be 36 mg/m^2.  A higher 43 mg/m² dose was initially tested but phase 1 data showed two cases of pneumonitis, a toxicity that will remain in focus.  

SVB analysts believe that the Uplift data will probably support approval in NaPi2b-high patients, but that a green light in all-comers is unlikely. Phase 1 updates showed shrinking efficacy across the overall study population. In NaPi2b–high patients the latest data cut from phase 1 showed 34% ORR, and median duration of response of ~5 months in 13 high expressors. 

Mersana has indicated that 12% ORR is the regulatory benchmark based on standard of care single-agent chemotherapies available in the setting. 

Cast off for Disc 

Disc Medicine’s bitopertin is an oral inhibitor of glycine transporter 1, which was previously developed by Roche. The big pharma group tried and failed to get the drug to work in schizophrenia and now Disc expects to report interim data in patients with erythropoietic porphyria (EPP) or X-linked protoporphyria (XLP), rare diseases characterised by extreme pain and damage to skin caused by light. Additionally, patients can suffer from liver impairment and gallstones. 

The Australian phase 2 Beacon study is due to report, and the primary endpoint of the open-label trial is the percent change from baseline in protoporphyrin IX (PPIX) concentration. A separate US placebo-controlled study called Aurora has the same endpoint and should report later in the year.  

Both EPP and XLP are caused by mutations in the genes that produce enzymes of the haem production pathway. These defects lead to abnormally high levels of PPIX in red blood cells. Bitopertin is said to work by reducing the activity of haem synthesis, and thus lowering the toxic build-up of metabolites such as PPIX.  

The only approved therapy for EPP is Clinuvel’s Scenesse, which increases skin melanin production to improve light tolerance. 

The table below contains a fuller list of upcoming catalysts with consensus forecasts from Evaluate Pharma.