I think this helps settling the argument for now (I think @Hodgie28 was right too re OS gold standard and PFS re product dev - IMO).

Below 1L means first line treatment. I note Efti is not 1L in AIPAC but still worth a read. So, yes,as we can see here, it it does no suggest IMM is being dodgy by reporting OS (and we don't know if it is not reporting PFS) !!!

Interestingly, the report you (@contrapuntal) initially pointed to, put critical weight on IMM for its transparency amongst some 6 companies (sellected out of 50) on listed on US and EU exchanges!!! But like I said, I just bin these reports, specially when it comes to evaluation.

Is progression-free survival a more relevant endpoint than overall survival in first-line HR+/HER2− metastatic breast cancer?

....

Conclusion

The goal of treatment in MBC is to prolong life while maintaining the quality of survival. As such, RCTs of MBC treatments ideally measure OS and HRQoL. In clinical trials of 1L therapies, OS is affected by multiple factors that cannot be controlled. This study examined important characteristics of RCTs in MBC and their relevance to OS. In addition to demographics, baseline characteristics, and prior adjuvant/neoadjuvant therapy, final OS is influenced by post-progression therapy and the total number of lines of therapy. This SLR found that ultimately very few 1L RCTs report OS improvement. PFS improvement is more often reported and its significance is perhaps understated. PFS, response rates, and QoL decrease as the disease progresses and with each line of therapy. PFS in 1L is an important predictor of PFS in further lines of therapy. In 1L treatments for MBC, PFS improvement coupled with maintained HRQoL provides patients with more meaningful time and may be considered the best possible outcome.

Source:

https://www.dovepress.com/is-progression-free-survival-a-more-relevant-endpoint-than-overall-sur-peer-reviewed-fulltext-article-CMAR#:~:text=Most%20importantly%2C%20PFS%20in%201L,of%20therapies%20among%20MBC%20patients.