Tubulis’ lead asset, TUB-040 is NaPi2b-targeting exatecan ADC emerges as a potentially differentiated contender in PROC, a setting characterized by poor outcomes and limited therapeutic options. Built on Tubulis’ proprietary ADC platform, TUB-040 combines a potent topoisomerase I inhibitor payload with a target that is broadly expressed across ovarian cancer, positioning it as a promising next-generation ADC with potential utility beyond biomarker-selected populations. 

The program has garnered significant industry validation through Tubulis’ strategic collaboration with Bristol Myers Squibb and was further strengthened by Gilead Sciences’ acquisition of the company in 2026, significantly expanding Gilead’s ADC capabilities through the addition of next-generation ADC assets and payload delivery platforms. Notably, the Phase I/II NAPISTAR 1-01 study demonstrated encouraging anti-tumor activity and a favorable tolerability profile without requiring patient selection based on NaPi2b expression or other biomarkers.

At ASCO 2026, updated NAPISTAR 1-01 trial data further reinforced TUB-040’s clinical potential PROC, demonstrating

Key Efficacy Highlights:

• Confirmed overall response rate (cORR): 60.9%, including 2 confirmed complete responses (cCRs)

• Unconfirmed overall response rate (uORR): 63.0%

• Disease control rate (DCR): 96.0%

• 90% of responses remained ongoing at data cutoff

• CA-125 response rate: 81.0% 

• Consistent activity across key subgroups:

• ≥4 prior lines of therapy: cORR 71%

• Prior bevacizumab: cORR 62%

• Prior PARP inhibitor (PARPi): cORR 67%

• Prior mirvetuximab soravtansine: cORR 63%

Key Safety Highlights: 

• 100% of patients experienced at least one treatment-related adverse event (TRAE)

• Grade 1 pneumonitis occurred in 6.5% of patients and resolved in all cases

• Most common all-grade TEAEs: nausea (78%), fatigue (54%), neutropenia (43.5%), anemia (37%), constipation (34%), diarrhea (33%), vomiting (28%), alopecia (28%), and decreased appetite (26%)

• No fatal TEAEs

• No treatment discontinuations due to TEAEs 

KOL insights:

“Current treatment options for PROC are limited by modest efficacy and poor durability. The NAPISTAR 1-01 trial data highlight the potential of NaPi2b-targeted ADCs, demonstrating strong clinical activity without biomarker selection, positioning TUB-040 as a promising new contender in PROC.”– Expert Opinion

“TUB-040’s differentiated design, featuring a highly stable linker–payload system, targets NaPi2b, a highly overexpressed transporter protein in ovarian cancer, supporting its rationale as a promising therapeutic approach in this setting.”– Expert Opinion 

Conclusion: 

Ovarian cancer remains one of the most lethal gynecologic malignancies, accounting for approximately 20,890 incident cases in the United States in 2025. The PROC landscape has evolved with the addition of bevacizumab (AVASTIN) and folate receptor alpha (FRα)-targeted ADCs such as mirvetuximab soravtansine (ELAHERE), while emerging agents including relacorilant, luveltamab and others are poised to intensify competition. In this increasingly crowded space, TUB-040, a novel NaPi2b-targeting exatecan ADC, demonstrated compelling efficacy in the Phase I/II NAPISTAR 1-01 study, achieving a 60.9% cOOR and 96.0% DCR with durable responses and a manageable safety profile in heavily pretreated patients. Given that NaPi2b is highly expressed in approximately 90% of ovarian cancers with minimal normal tissue expression, TUB-040 is well positioned as a differentiated next-generation ADC with the potential to further intensify competition and raise the efficacy benchmark in PROC.